Presented by: Ashwin (Microsoft Azure MVP)
Bandook is a commercially available RAT, written in Delphi and C++, that has been available since at least 2007. It has been used against government, financial, energy, healthcare, education, IT, and legal organizations in the US, South America, Europe, and Southeast Asia. Bandook has been used by Dark Caracal, as well as in a separate campaign referred to as "Operation Manul".
Source:
MITRE ATT&CK® Matrix for Enterprise
Now, let's see the details around the series of events associated with this software in chronological order, and how we can work to mitigate or detect these threats.
Bandook is delivered via a malicious Word document inside a zip file.
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.
Bandook can support commands to execute Java-based payloads.
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.
Bandook has used PowerShell loaders as part of execution.
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.
Bandook is capable of spawning a Windows command shell.
Adversaries may abuse the Windows command shell for execution. The Windows command shell (cmd) is the primary command prompt on Windows systems. The Windows command prompt can be used to control almost any aspect of a system, with various permission levels required for different subsets of commands. The command prompt can be invoked remotely via Remote Services such as SSH.
Batch files (ex: .bat or .cmd) also provide the shell with a list of sequential commands to run, as well as normal scripting operations such as conditionals and loops. Common uses of batch files include long or repetitive tasks, or the need to run the same set of commands on multiple systems.
Adversaries may leverage cmd to execute various commands and payloads. Common uses include cmd to execute a single command, or abusing cmd interactively with input and output forwarded over a command and control channel.
Execution Prevention
Use application control 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)
Monitor executed commands and arguments that may abuse the Windows command shell for execution. Usage of the Windows command shell may be common on administrator, developer, or power user systems depending on job function. If scripting is restricted for normal users, then any attempt 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.
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 the Windows command shell for execution.
Bandook has used malicious VBA code against the target system.
Adversaries may abuse Visual Basic (VB) for execution. VB is a programming language created by Microsoft with interoperability with many Windows technologies such as Component Object Model and the Native API through the Windows API. Although tagged as legacy with no planned future evolutions, VB is integrated and supported in the .NET Framework and cross-platform .NET Core.
Derivative languages based on VB have also been created, such as Visual Basic for Applications (VBA) and VBScript. VBA is an event-driven programming language built into Microsoft Office, as well as several third-party applications. VBA enables documents to contain macros used to automate the execution of tasks and other functionality on the host. VBScript is a default scripting language on Windows hosts and can also be used in place of JavaScript on HTML Application (HTA) webpages served to Internet Explorer (though most modern browsers do not come with VBScript support).
Adversaries may use VB payloads to execute malicious commands. Common malicious usage includes automating execution of behaviors with VBScript or embedding VBA content into Spearphishing Attachment payloads (which may also involve Mark-of-the-Web Bypass to enable 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 scripts from executing potentially malicious downloaded content.
Disable or Remove Feature or Program
Turn off or restrict access to unneeded VB components.
Execution Prevention
Use application control where appropriate. VBA macros obtained from the Internet, based on the file's Mark of the Web (MOTW) attribute, may be blocked from executing in Office applications (ex: Access, Excel, PowerPoint, Visio, and Word) by default starting in Windows Version 2203.
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 executed commands and arguments that may abuse Visual Basic (VB) for execution.
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 the loading of modules associated with VB languages (ex: vbscript.dll).
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for events associated with VB execution, such as Office applications spawning processes, usage of the Windows Script Host (typically cscript.exe or wscript.exe). VB execution is likely to perform actions with various effects on a system that may generate events, depending on the types of monitoring used.
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.
Bandook can support commands to execute Python-based payloads.
Adversaries may abuse Python commands and scripts for execution. Python is a very popular scripting/programming language, with capabilities to perform many functions. Python can be executed interactively from the command-line (via the python.exe interpreter) or via scripts (.py) that can be written and distributed to different systems. Python code can also be compiled into binary executables.
Python comes with many built-in packages to interact with the underlying system, such as file operations and device I/O. Adversaries can use these libraries to download and execute commands or other scripts as well as perform various malicious behaviors.
Antivirus/Antimalware
Anti-virus can be used to automatically quarantine suspicious files.
Audit
Inventory systems for unauthorized Python installations.
Execution Prevention
Denylist Python where not required.
Limit Software Installation
Prevent users from installing Python where not required.
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 systems for abnormal Python usage and python.exe behavior, which could be an indicator of malicious activity. Understanding standard usage patterns is important to avoid a high number of false positives. If scripting is restricted for normal users, then 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. Scripts are likely to perform actions with various effects on a system that may generate events, depending on the types of monitoring used. Monitor executed commands and arguments that may abuse Python commands and scripts for execution.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor systems for abnormal Python usage and python.exe behavior, which could be an indicator of malicious activity. Understanding standard usage patterns is important to avoid a high number of false positives. If scripting is restricted for normal users, then 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. Scripts are likely to perform actions with various effects on a system that may generate events, depending on the types of monitoring used. Monitor newly executed processes that may abuse Python commands and scripts for execution.
Bandook has used the ShellExecuteW() function call.
Adversaries may interact with the native OS application programming interface (API) to execute behaviors. Native APIs provide a controlled means of calling low-level OS services within the kernel, such as those involving hardware/devices, memory, and processes. These native APIs are leveraged by the OS during system boot (when other system components are not yet initialized) as well as carrying out tasks and requests during routine operations.
Native API functions (such as NtCreateProcess) may be directed invoked via system calls / syscalls, but these features are also often exposed to user-mode applications via interfaces and libraries. For example, functions such as the Windows API CreateProcess() or GNU fork() will allow programs and scripts to start other processes. This may allow API callers to execute a binary, run a CLI command, load modules, etc. as thousands of similar API functions exist for various system operations.
Higher level software frameworks, such as Microsoft .NET and macOS Cocoa, are also available to interact with native APIs. These frameworks typically provide language wrappers/abstractions to API functionalities and are designed for ease-of-use/portability of code.
Adversaries may abuse these OS API functions as a means of executing behaviors. Similar to Command and Scripting Interpreter, the native API and its hierarchy of interfaces provide mechanisms to interact with and utilize various components of a victimized system. While invoking API functions, adversaries may also attempt to bypass defensive tools (ex: unhooking monitored functions via Disable or Modify Tools).
Behavior Prevention on Endpoint
On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent Office VBA macros from calling Win32 APIs.
Execution Prevention
Identify and block potentially malicious software executed that may be executed through this technique 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.
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. Utilization of the Windows APIs may involve processes loading/accessing system DLLs associated with providing called functions (ex: ntdll.dll, kernel32.dll, advapi32.dll, user32.dll, and gdi32.dll). Monitoring for DLL loads, especially to abnormal/unusual or potentially malicious processes, may indicate abuse of the Windows API. Though noisy, this data can be combined with other indicators to identify adversary activity.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitoring API calls may generate a significant amount of data and may not be useful for defense unless collected under specific circumstances, since benign use of API functions are common and may be difficult to distinguish from malicious behavior. Correlation of other events with behavior surrounding API function calls using API monitoring will provide additional context to an event that may assist in determining if it is due to malicious behavior. Correlation of activity by process lineage by process ID may be sufficient.
Bandook has used lure documents to convince the user to enable macros.
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.
Bandook has been launched by starting iexplore.exe and replacing it with Bandook's payload.
Adversaries may inject malicious code into suspended and hollowed processes in order to evade process-based defenses. Process hollowing is a method of executing arbitrary code in the address space of a separate live process.
Process hollowing is commonly performed by creating a process in a suspended state then unmapping/hollowing its memory, which can then be replaced with malicious code. A victim process can be created with native Windows API calls such as CreateProcess, which includes a flag to suspend the processes primary thread. At this point the process can be unmapped using APIs calls such as ZwUnmapViewOfSection or NtUnmapViewOfSection before being written to, realigned to the injected code, and resumed via VirtualAllocEx, WriteProcessMemory, SetThreadContext, then ResumeThread respectively.
This is very similar to Thread Local Storage but creates a new process rather than targeting an existing process. This behavior will likely not result in elevated privileges since the injected process was spawned from (and thus inherits the security context) of the injecting process. However, execution via process hollowing may also evade detection from security products since the execution is masked under a legitimate process.
Behavior Prevention on Endpoint
Some endpoint security solutions can be configured to block some types of process injection based on common sequences of behavior that occur during the injection process.
Monitoring the following activities in your Organization can help you detect this technique.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitoring Windows API calls indicative of the various types of code injection may generate a significant amount of data and may not be directly useful for defense unless collected under specific circumstances for known bad sequences of calls, since benign use of API functions may be common and difficult to distinguish from malicious behavior. Windows API calls such as CreateRemoteThread, SuspendThread/SetThreadContext/ResumeThread, and those that can be used to modify memory within another process, such as VirtualAllocEx/WriteProcessMemory, may be used for this technique.
Process: Process Access
Opening of a process by another process, typically to read memory of the target process (ex: Sysmon EID 10)
Monitor for processes being viewed that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses.
Process: Process Modification
Changes made to a process, or its contents, typically to write and/or execute code in the memory of the target process (ex: Sysmon EID 8)
Monitor for changes made to processes that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses.
Bandook has used .PNG images within a zip file to build the executable.
Adversaries may use steganography techniques in order to prevent the detection of hidden information. Steganographic techniques can be used to hide data in digital media such as images, audio tracks, video clips, or text files.
Duqu was an early example of malware that used steganography. It encrypted the gathered information from a victim's system and hid it within an image before exfiltrating the image to a C2 server.
By the end of 2017, a threat group used Invoke-PSImage to hide PowerShell commands in an image file (.png) and execute the code on a victim's system. In this particular case the PowerShell code downloaded another obfuscated script to gather intelligence from the victim's machine and communicate it back to 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 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.
Detection of steganography is difficult unless artifacts are left behind by the obfuscation process that are detectable with a known signature. Look for strings or other signatures left in system artifacts related to decoding steganography.
Bandook has been launched by starting iexplore.exe and replacing it with Bandook's payload.
Adversaries may inject malicious code into suspended and hollowed processes in order to evade process-based defenses. Process hollowing is a method of executing arbitrary code in the address space of a separate live process.
Process hollowing is commonly performed by creating a process in a suspended state then unmapping/hollowing its memory, which can then be replaced with malicious code. A victim process can be created with native Windows API calls such as CreateProcess, which includes a flag to suspend the processes primary thread. At this point the process can be unmapped using APIs calls such as ZwUnmapViewOfSection or NtUnmapViewOfSection before being written to, realigned to the injected code, and resumed via VirtualAllocEx, WriteProcessMemory, SetThreadContext, then ResumeThread respectively.
This is very similar to Thread Local Storage but creates a new process rather than targeting an existing process. This behavior will likely not result in elevated privileges since the injected process was spawned from (and thus inherits the security context) of the injecting process. However, execution via process hollowing may also evade detection from security products since the execution is masked under a legitimate process.
Behavior Prevention on Endpoint
Some endpoint security solutions can be configured to block some types of process injection based on common sequences of behavior that occur during the injection process.
Monitoring the following activities in your Organization can help you detect this technique.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitoring Windows API calls indicative of the various types of code injection may generate a significant amount of data and may not be directly useful for defense unless collected under specific circumstances for known bad sequences of calls, since benign use of API functions may be common and difficult to distinguish from malicious behavior. Windows API calls such as CreateRemoteThread, SuspendThread/SetThreadContext/ResumeThread, and those that can be used to modify memory within another process, such as VirtualAllocEx/WriteProcessMemory, may be used for this technique.
Process: Process Access
Opening of a process by another process, typically to read memory of the target process (ex: Sysmon EID 10)
Monitor for processes being viewed that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses.
Process: Process Modification
Changes made to a process, or its contents, typically to write and/or execute code in the memory of the target process (ex: Sysmon EID 8)
Monitor for changes made to processes that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses.
Bandook has a command to delete a file.
Adversaries may delete files left behind by the actions of their intrusion activity. Malware, tools, or other non-native files dropped or created on a system by an adversary (ex: Ingress Tool Transfer) may leave traces to indicate to what was done within a network and how. Removal of these files can occur during an intrusion, or as part of a post-intrusion process to minimize the adversary's footprint.
There are tools available from the host operating system to perform cleanup, but adversaries may use other tools as well. Examples of built-in Command and Scripting Interpreter functions include del on Windows and rm or unlink on Linux and macOS.
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 for actions that could be utilized to unlink, rename, or delete files.
File: File Deletion
Removal of a file (ex: Sysmon EID 23, macOS ESF EID ES_EVENT_TYPE_AUTH_UNLINK, or Linux commands auditd unlink, rename, rmdir, unlinked, or renameat rules)
Monitor for unexpected deletion of files from the system
Bandook has decoded its PowerShell script.
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.
Bandook was signed with valid Certum certificates.
Adversaries may create, acquire, or steal code signing materials to sign their malware or tools. Code signing provides a level of authenticity on a binary from the developer and a guarantee that the binary has not been tampered with. The certificates used during an operation may be created, acquired, or stolen by the adversary. Unlike Invalid Code Signature, this activity will result in a valid signature.
Code signing to verify software on first run can be used on modern Windows and macOS/OS X systems. It is not used on Linux due to the decentralized nature of the platform.
Code signing certificates may be used to bypass security policies that require signed code to execute on a system.
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 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.
Collect and analyze signing certificate metadata on software that executes within the environment to look for unusual certificate characteristics and outliers.
Bandook contains keylogging capabilities.
Adversaries may log user keystrokes to intercept credentials as the user types them. Keylogging is likely to be used to acquire credentials for new access opportunities when OS Credential Dumping efforts are not effective, and may require an adversary to intercept keystrokes on a system for a substantial period of time before credentials can be successfully captured.
Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes. Some methods include:
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.
Driver: Driver Load
Attaching a driver to either user or kernel-mode of a system (ex: Sysmon EID 6)
Monitor for unusual kernel driver installation activity
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 to the SetWindowsHook, GetKeyState, and GetAsyncKeyState. and look for common keylogging API calls. API calls alone are not an indicator of keylogging, but may provide behavioral data that is useful when combined with other information such as new files written to disk and unusual processes.
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 for unexpected modifications
Bandook has a command to get the public IP address from a system.
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.
Bandook can collect information about the drives available on the system.
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.
Bandook has a command to list files on a system.
Adversaries may enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system. Adversaries may use the information from File and Directory Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.
Many command shell utilities can be used to obtain this information. Examples include dir, tree, ls, find, and locate. Custom tools may also be used to gather file and directory information and interact with the Native API. Adversaries may also leverage a Network Device CLI on network devices to gather file and directory 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.
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 enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system.
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 enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor newly executed processes that may enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system.
Bandook can detect USB devices.
Adversaries may attempt to gather information about attached peripheral devices and components connected to a computer system. Peripheral devices could include auxiliary resources that support a variety of functionalities such as keyboards, printers, cameras, smart card readers, or removable storage. The information may be used to enhance their awareness of the system and network environment or may be used for further actions.
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 gather information about attached peripheral devices and components connected to a computer system.
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 gather information about attached peripheral devices and components connected to a computer system.
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 gather information about attached peripheral devices and components connected to a computer system.
Bandook can collect local files from the system .
Adversaries may search local system sources, such as file systems and configuration files or local databases, to find files of interest and sensitive data prior to Exfiltration.
Adversaries may do this using a Command and Scripting Interpreter, such as cmd as well as a Network Device CLI, which have functionality to interact with the file system to gather information. Adversaries may also use Automated Collection on the local system.
Data Loss Prevention
Data loss prevention can restrict access to sensitive data and detect sensitive data that is unencrypted.
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 search and collect local system sources, such as file systems or local databases, to find files of interest and sensitive data prior to Exfiltration. Remote access tools with built-in features may interact directly with the Windows API to gather data. Data may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell.
File: File Access
Opening a file, which makes the file contents available to the requestor (ex: Windows EID 4663)
Monitor for unexpected/abnormal access to files that may be malicious collection of local data, such as user files (pdf, .docx, .jpg, etc.) or local databases.
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 search local system sources, such as file systems or local databases, to find files of interest and sensitive data prior to Exfiltration.
Process: Process Creation
Birth of a new running process (ex: Sysmon EID 1 or Windows EID 4688)
Monitor for newly executed processes that may search local system sources, such as file systems or local databases, to find files of interest and sensitive data prior to Exfiltration.
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. Data may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell.
Bandook contains keylogging capabilities.
Adversaries may log user keystrokes to intercept credentials as the user types them. Keylogging is likely to be used to acquire credentials for new access opportunities when OS Credential Dumping efforts are not effective, and may require an adversary to intercept keystrokes on a system for a substantial period of time before credentials can be successfully captured.
Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes. Some methods include:
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.
Driver: Driver Load
Attaching a driver to either user or kernel-mode of a system (ex: Sysmon EID 6)
Monitor for unusual kernel driver installation activity
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 to the SetWindowsHook, GetKeyState, and GetAsyncKeyState. and look for common keylogging API calls. API calls alone are not an indicator of keylogging, but may provide behavioral data that is useful when combined with other information such as new files written to disk and unusual processes.
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 for unexpected modifications
Bandook is capable of taking an image of and uploading the current desktop.
Adversaries may attempt to take screen captures of the desktop to gather information over the course of an operation. Screen capturing functionality may be included as a feature of a remote access tool used in post-compromise operations. Taking a screenshot is also typically possible through native utilities or API calls, such as CopyFromScreen, xwd, or screencapture.
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 take screen captures of the desktop to gather information over the course of an operation.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Monitoring for screen capture behavior will depend on the method used to obtain data from the operating system and write output files. Detection methods could include collecting information from unusual processes using API calls used to obtain image data, and monitoring for image files written to disk, such as CopyFromScreen, xwd, or screencapture. The sensor data may need to be correlated with other events to identify malicious activity, depending on the legitimacy of this behavior within a given network environment.
Bandook has modules that are capable of capturing audio.
An adversary can leverage a computer's peripheral devices (e.g., microphones and webcams) or applications (e.g., voice and video call services) to capture audio recordings for the purpose of listening into sensitive conversations to gather information.
Malware or scripts may be used to interact with the devices through an available API provided by the operating system or an application to capture audio. Audio files may be written to disk and exfiltrated later.
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 for actions that can leverage a computer’s peripheral devices (e.g., microphones and webcams) or applications (e.g., voice and video call services) to capture audio recordings for the purpose of listening into sensitive conversations to gather information.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Bandook has modules that are capable of capturing video from a victim's webcam.
An adversary can leverage a computer's peripheral devices (e.g., integrated cameras or webcams) or applications (e.g., video call services) to capture video recordings for the purpose of gathering information. Images may also be captured from devices or applications, potentially in specified intervals, in lieu of video files.
Malware or scripts may be used to interact with the devices through an available API provided by the operating system or an application to capture video or images. Video or image files may be written to disk and exfiltrated later. This technique differs from Screen Capture due to use of specific devices or applications for video recording rather than capturing the victim's screen.
In macOS, there are a few different malware samples that record the user's webcam such as FruitFly and Proton.
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 can leverage a computer's peripheral devices (e.g., integrated cameras or webcams) or applications (e.g., video call services) to capture video recordings for the purpose of gathering information.
Process: OS API Execution
Initial construction of a WMI object, such as a filter, consumer, subscription, binding, or provider (ex: Sysmon EIDs 19-21)
Detection of this technique may be difficult due to the various APIs that may be used. Telemetry data regarding API use may not be useful depending on how a system is normally used, but may provide context to other potentially malicious activity occurring on a system. Behavior that could indicate technique use include an unknown or unusual process accessing APIs associated with devices or software that interact with the video camera, recording devices, or recording software, and a process periodically writing files to disk that contain video or camera image data.
Bandook has a command built in to use a raw TCP socket.
Adversaries may use a non-application layer protocol for communication between host and C2 server or among infected hosts within a network. The list of possible protocols is extensive. Specific examples include use of network layer protocols, such as the Internet Control Message Protocol (ICMP), transport layer protocols, such as the User Datagram Protocol (UDP), session layer protocols, such as Socket Secure (SOCKS), as well as redirected/tunneled protocols, such as Serial over LAN (SOL).
ICMP communication between hosts is one example. Because ICMP is part of the Internet Protocol Suite, it is required to be implemented by all IP-compatible hosts. However, it is not as commonly monitored as other Internet Protocols such as TCP or UDP and may be used by adversaries to hide communications.
Filter Network Traffic
Filter network traffic to prevent use of protocols across the network boundary that are unnecessary.
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.
Network Segmentation
Properly configure firewalls and proxies to limit outgoing traffic to only necessary ports and through proper network gateway systems. Also ensure hosts are only provisioned to communicate over authorized interfaces.
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) 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.
Bandook can download files to the system.
Adversaries may transfer tools or other files from an external system into a compromised environment. Tools or files may be copied from an external adversary-controlled system to the victim network through the command and control channel or through alternate protocols such as ftp. Once present, adversaries may also transfer/spread tools between victim devices within a compromised environment (i.e. Lateral Tool Transfer).
Files can also be transferred using various Web Services as well as native or otherwise present tools on the victim system.
On Windows, adversaries may use various utilities to download tools, such as copy, finger, and PowerShell commands such as IEX(New-Object Net.WebClient).downloadString() and Invoke-WebRequest. On Linux and macOS systems, a variety of utilities also exist, such as curl, scp, sftp, tftp, rsync, finger, and wget.
Network Intrusion Prevention
Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware or unusual data transfer over known protocols like FTP 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.
File: File Creation
Initial construction of a new file (ex: Sysmon EID 11)
Monitor for file creation and files transferred into the network
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 or creating files on-system may be suspicious. Use of utilities, such as FTP, that does not normally occur may also be suspicious.
Network Traffic: Network Traffic Content
Logged network traffic data showing both protocol header and body values (ex: PCAP)
Monitor network traffic content for files and other potentially malicious content, especially data coming in from abnormal/unknown domain and IPs.
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 (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.
Bandook has used AES encryption for C2 communication.
Adversaries may employ a known symmetric encryption algorithm to conceal command and control traffic rather than relying on any inherent protections provided by a communication protocol. Symmetric encryption algorithms use the same key for plaintext encryption and ciphertext decryption. Common symmetric encryption algorithms include AES, DES, 3DES, Blowfish, and RC4.
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) 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)).
Bandook can upload files from a victim's machine over the C2 channel.
Adversaries may steal data by exfiltrating it over an existing command and control channel. Stolen data is encoded into the normal communications channel using the same protocol as command and control communications.
Data Loss Prevention
Data loss prevention can detect and block sensitive data being sent over unencrypted protocols.
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 command and control signatures over time or construct protocols in such a way to avoid detection by common defensive tools.
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 steal data by exfiltrating it over an existing command and control channel.
File: File Access
Opening a file, which makes the file contents available to the requestor (ex: Windows EID 4663)
Monitor for suspicious files (i.e. .pdf, .docx, .jpg, etc.) viewed in isolation that may steal data by exfiltrating it over an existing command and control channel.
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 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.
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