Presented by: Ashwin (Microsoft Azure MVP)
BONDUPDATER is a PowerShell backdoor used by OilRig. It was first observed in November 2017 during targeting of a Middle Eastern government organization, and an updated version was observed in August 2018 being used to target a government organization with spearphishing emails.
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.
BONDUPDATER persists using a scheduled task that executes every minute.
Adversaries may abuse the Windows Task Scheduler to perform task scheduling for initial or recurring execution of malicious code. There are multiple ways to access the Task Scheduler in Windows. The schtasks utility can be run directly on the command line, or the Task Scheduler can be opened through the GUI within the Administrator Tools section of the Control Panel. In some cases, adversaries have used a .NET wrapper for the Windows Task Scheduler, and alternatively, adversaries have used the Windows netapi32 library to create a scheduled task.
The deprecated at utility could also be abused by adversaries (ex: At), though at.exe can not access tasks created with schtasks or the Control Panel.
An adversary may use Windows Task Scheduler to execute programs at system startup or on a scheduled basis for persistence. The Windows Task Scheduler can also be abused to conduct remote Execution as part of Lateral Movement and/or to run a process under the context of a specified account (such as SYSTEM). Similar to System Binary Proxy Execution, adversaries have also abused the Windows Task Scheduler to potentially mask one-time execution under signed/trusted system processes.
Audit
Toolkits like the PowerSploit framework contain PowerUp modules that can be used to explore systems for permission weaknesses in scheduled tasks that could be used to escalate privileges.
Operating System Configuration
Configure settings for scheduled tasks to force tasks to run under the context of the authenticated account instead of allowing them to run as SYSTEM. The associated Registry key is located at HKLM\SYSTEM\CurrentControlSet\Control\Lsa\SubmitControl. The setting can be configured through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > Security Options: Domain Controller: Allow server operators to schedule tasks, set to disabled.
Privileged Account Management
Configure the Increase Scheduling Priority option to only allow the Administrators group the rights to schedule a priority process. This can be configured through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > User Rights Assignment: Increase scheduling priority.
User Account Management
Limit privileges of user accounts and remediate Privilege Escalation vectors so only authorized administrators can create scheduled tasks on remote systems.
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 gather tasks may also be created 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.
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 Windows Task Scheduler stores in %systemroot%\System32\Tasks for change entries related to scheduled tasks that do not correlate with known software, patch cycles, etc.
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 that execute from the svchost.exe in Windows 10 and the Windows Task Scheduler taskeng.exe for older versions of Windows. If scheduled tasks are not used for persistence, then the adversary is likely to remove the task when the action is complete.
Scheduled Job: Scheduled Job Creation
Initial construction of a new scheduled job (ex: Windows EID 4698 or /var/log cron logs)
Monitor for newly constructed scheduled jobs by enabling the "Microsoft-Windows-TaskScheduler/Operational" setting within the event logging service. Several events will then be logged on scheduled task activity, including: Event ID 106 on Windows 7, Server 2008 R2 - Scheduled task registered; Event ID 4698 on Windows 10, Server 2016 - Scheduled task created;Event ID 4700 on Windows 10, Server 2016 - Scheduled task enabled;Event ID 4701 on Windows 10, Server 2016 - Scheduled task disabled
BONDUPDATER is written in PowerShell.
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.
BONDUPDATER can read batch commands in a file sent from its C2 server and execute them with cmd.exe.
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.
BONDUPDATER persists using a scheduled task that executes every minute.
Adversaries may abuse the Windows Task Scheduler to perform task scheduling for initial or recurring execution of malicious code. There are multiple ways to access the Task Scheduler in Windows. The schtasks utility can be run directly on the command line, or the Task Scheduler can be opened through the GUI within the Administrator Tools section of the Control Panel. In some cases, adversaries have used a .NET wrapper for the Windows Task Scheduler, and alternatively, adversaries have used the Windows netapi32 library to create a scheduled task.
The deprecated at utility could also be abused by adversaries (ex: At), though at.exe can not access tasks created with schtasks or the Control Panel.
An adversary may use Windows Task Scheduler to execute programs at system startup or on a scheduled basis for persistence. The Windows Task Scheduler can also be abused to conduct remote Execution as part of Lateral Movement and/or to run a process under the context of a specified account (such as SYSTEM). Similar to System Binary Proxy Execution, adversaries have also abused the Windows Task Scheduler to potentially mask one-time execution under signed/trusted system processes.
Audit
Toolkits like the PowerSploit framework contain PowerUp modules that can be used to explore systems for permission weaknesses in scheduled tasks that could be used to escalate privileges.
Operating System Configuration
Configure settings for scheduled tasks to force tasks to run under the context of the authenticated account instead of allowing them to run as SYSTEM. The associated Registry key is located at HKLM\SYSTEM\CurrentControlSet\Control\Lsa\SubmitControl. The setting can be configured through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > Security Options: Domain Controller: Allow server operators to schedule tasks, set to disabled.
Privileged Account Management
Configure the Increase Scheduling Priority option to only allow the Administrators group the rights to schedule a priority process. This can be configured through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > User Rights Assignment: Increase scheduling priority.
User Account Management
Limit privileges of user accounts and remediate Privilege Escalation vectors so only authorized administrators can create scheduled tasks on remote systems.
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 gather tasks may also be created 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.
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 Windows Task Scheduler stores in %systemroot%\System32\Tasks for change entries related to scheduled tasks that do not correlate with known software, patch cycles, etc.
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 that execute from the svchost.exe in Windows 10 and the Windows Task Scheduler taskeng.exe for older versions of Windows. If scheduled tasks are not used for persistence, then the adversary is likely to remove the task when the action is complete.
Scheduled Job: Scheduled Job Creation
Initial construction of a new scheduled job (ex: Windows EID 4698 or /var/log cron logs)
Monitor for newly constructed scheduled jobs by enabling the "Microsoft-Windows-TaskScheduler/Operational" setting within the event logging service. Several events will then be logged on scheduled task activity, including: Event ID 106 on Windows 7, Server 2008 R2 - Scheduled task registered; Event ID 4698 on Windows 10, Server 2016 - Scheduled task created;Event ID 4700 on Windows 10, Server 2016 - Scheduled task enabled;Event ID 4701 on Windows 10, Server 2016 - Scheduled task disabled
BONDUPDATER persists using a scheduled task that executes every minute.
Adversaries may abuse the Windows Task Scheduler to perform task scheduling for initial or recurring execution of malicious code. There are multiple ways to access the Task Scheduler in Windows. The schtasks utility can be run directly on the command line, or the Task Scheduler can be opened through the GUI within the Administrator Tools section of the Control Panel. In some cases, adversaries have used a .NET wrapper for the Windows Task Scheduler, and alternatively, adversaries have used the Windows netapi32 library to create a scheduled task.
The deprecated at utility could also be abused by adversaries (ex: At), though at.exe can not access tasks created with schtasks or the Control Panel.
An adversary may use Windows Task Scheduler to execute programs at system startup or on a scheduled basis for persistence. The Windows Task Scheduler can also be abused to conduct remote Execution as part of Lateral Movement and/or to run a process under the context of a specified account (such as SYSTEM). Similar to System Binary Proxy Execution, adversaries have also abused the Windows Task Scheduler to potentially mask one-time execution under signed/trusted system processes.
Audit
Toolkits like the PowerSploit framework contain PowerUp modules that can be used to explore systems for permission weaknesses in scheduled tasks that could be used to escalate privileges.
Operating System Configuration
Configure settings for scheduled tasks to force tasks to run under the context of the authenticated account instead of allowing them to run as SYSTEM. The associated Registry key is located at HKLM\SYSTEM\CurrentControlSet\Control\Lsa\SubmitControl. The setting can be configured through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > Security Options: Domain Controller: Allow server operators to schedule tasks, set to disabled.
Privileged Account Management
Configure the Increase Scheduling Priority option to only allow the Administrators group the rights to schedule a priority process. This can be configured through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > User Rights Assignment: Increase scheduling priority.
User Account Management
Limit privileges of user accounts and remediate Privilege Escalation vectors so only authorized administrators can create scheduled tasks on remote systems.
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 gather tasks may also be created 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.
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 Windows Task Scheduler stores in %systemroot%\System32\Tasks for change entries related to scheduled tasks that do not correlate with known software, patch cycles, etc.
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 that execute from the svchost.exe in Windows 10 and the Windows Task Scheduler taskeng.exe for older versions of Windows. If scheduled tasks are not used for persistence, then the adversary is likely to remove the task when the action is complete.
Scheduled Job: Scheduled Job Creation
Initial construction of a new scheduled job (ex: Windows EID 4698 or /var/log cron logs)
Monitor for newly constructed scheduled jobs by enabling the "Microsoft-Windows-TaskScheduler/Operational" setting within the event logging service. Several events will then be logged on scheduled task activity, including: Event ID 106 on Windows 7, Server 2008 R2 - Scheduled task registered; Event ID 4698 on Windows 10, Server 2016 - Scheduled task created;Event ID 4700 on Windows 10, Server 2016 - Scheduled task enabled;Event ID 4701 on Windows 10, Server 2016 - Scheduled task disabled
BONDUPDATER uses -windowstyle hidden to conceal a PowerShell window that downloads a payload.
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.
BONDUPDATER can use DNS and TXT records within its DNS tunneling protocol for command and control.
Adversaries may communicate using the Domain Name System (DNS) application layer protocol 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.
The DNS protocol serves an administrative function in computer networking and thus may be very common in environments. DNS traffic may also be allowed even before network authentication is completed. DNS packets contain many fields and headers in which data can be concealed. Often known as DNS tunneling, adversaries may abuse DNS to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.
Filter Network Traffic
Consider filtering DNS requests to unknown, untrusted, or known bad domains and resources. Resolving DNS requests with on-premise/proxy servers may also disrupt adversary attempts to conceal data within DNS packets.
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 DNSSEC 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 DNS 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)).
BONDUPDATER can download or upload files from its C2 server.
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.
BONDUPDATER uses a DGA to communicate with command and control servers.
Adversaries may make use of Domain Generation Algorithms (DGAs) to dynamically identify a destination domain for command and control traffic rather than relying on a list of static IP addresses or domains. This has the advantage of making it much harder for defenders to block, track, or take over the command and control channel, as there potentially could be thousands of domains that malware can check for instructions.
DGAs can take the form of apparently random or "gibberish" strings (ex: istgmxdejdnxuyla.ru) when they construct domain names by generating each letter. Alternatively, some DGAs employ whole words as the unit by concatenating words together instead of letters (ex: cityjulydish.net). Many DGAs are time-based, generating a different domain for each time period (hourly, daily, monthly, etc). Others incorporate a seed value as well to make predicting future domains more difficult for defenders.
Adversaries may use DGAs for the purpose of Fallback Channels. When contact is lost with the primary command and control server malware may employ a DGA as a means to reestablishing command and control.
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. Malware researchers can reverse engineer malware variants that use DGAs and determine future domains that the malware will attempt to contact, but this is a time and resource intensive effort. Malware is also increasingly incorporating seed values that can be unique for each instance, which would then need to be determined to extract future generated domains. In some cases, the seed that a particular sample uses can be extracted from DNS traffic. Even so, there can be thousands of possible domains generated per day; this makes it impractical for defenders to preemptively register all possible C2 domains due to the cost.
Restrict Web-Based Content
In some cases a local DNS sinkhole may be used to help prevent DGA-based command and control at a reduced cost.
Monitoring the following activities in your Organization can help you detect this technique.
Network Traffic: Network Traffic Flow
Summarized network packet data, with metrics, such as protocol headers and volume (ex: Netflow or Zeek http.log)
Detecting dynamically generated domains can be challenging due to the number of different DGA algorithms, constantly evolving malware families, and the increasing complexity of the algorithms. There is a myriad of approaches for detecting a pseudo-randomly generated domain name, including using frequency analysis, Markov chains, entropy, proportion of dictionary words, ratio of vowels to other characters, and more. CDN domains may trigger these detections due to the format of their domain names. In addition to detecting a DGA domain based on the name, another more general approach for detecting a suspicious domain is to check for recently registered names or for rarely visited domains.Machine learning approaches to detecting DGA domains have been developed and have seen success in applications. One approach is to use N-Gram methods to determine a randomness score for strings used in the domain name. If the randomness score is high, and the domains are not whitelisted (CDN, etc), then it may be determined if a domain is related to a legitimate host or DGA. Another approach is to use deep learning to classify domains as DGA-generated]
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