![]() ![]() Note that the reg.exe command are only run if the script is being executed as a non-admin. The following commands are run when Invisi-Shell starts. This detection identifies the use of Invisi-Shell, a method of running PowerShell without any of the normal security features that come with PowerShell (ScriptBlock logging, Module logging, Transcription, AMSI). If this activity is not benign or expected, consider rebuilding the host from a known, good source and having the user change their password. Examine the parent process that spawned the command, and anything else that process may have spawned. RecommendationĪcquire the INF file that is being installed and analyze for suspicious contents in the DefaultInstall_SingleUser and UnRegisterOCX sections. Under this section, the OCX unregister directive, UnRegisterOCXs, calls the UnRegisterOCXSection to perform the ‘malicious’ action of invoking scrobj.dll to fetch and run the SCT script file. Within the source INF file used for remote SCT execution, ‘cmstp.exe’ calls the INF section named ‘DefaultInstall_SingleUser’. For reference, basic usage for ‘cmstp.exe’ is as follows: Malicious actors can use INF files to fetch SCT files from web resources and execute COM scripts/scriptlets using ‘cmstp.exe’, which is a utility that is able to bypass UAC and AppLocker default policies. This detection identifies the use of CMSTP to load an INF file. Obfuscated Files or Information - T1027.If necessary, rebuild the host from a known, good source and have the user change their password. Investigate the user's inbox to identify any malicious emails, and determine if any other users received the email. The source could be a malicious document sent by a malicious actor to the user by email. RecommendationĪcquire additional process artifacts and identify the root cause of the suspicious process invocation. The executed file is visible within the command line parameters of the process start event. This technique is used by malicious actors to subvert antivirus and other defensive countermeasures. ![]() This detection identifies Microsoft Office processes spawning ‘MSBuild.exe’, which is the result of various droppers or downloaders using ‘MSBuild.exe’ to compile and execute arbitrary code. Command and Scripting Interpreter - T1059.Malicious actors use phishing emails to send malicious documents. Other methods to execute malicious code in an Office document include using Dynamic Data Exchange objects or exploiting software vulnerabilities. Macros run commands using built-in Windows utilities, such as PowerShell, to download malware and compromise the system. These malicious documents leverage macros, which are small Visual Basic for Applications (VBA) scripts embedded inside of Microsoft Office documents, such as PowerPoint, Excel and Word. This detection identifies suspicious processes spawned by Microsoft Office applications, which could indicate that a malicious actor is using a malicious document. Review the URL passed to 'mshta.exe' to determine if it is from a trusted source., Review the firewall and web proxy logs from this endpoint to identify any malware retrieval from remote systems. Review the firewall and web proxy logs from this endpoint to identify any malware retrieval from remote systems. A malicious actor could pass commands to PowerShell obfuscated or encoded using compression tools, such as Base64 or gzip. Review the command passed to PowerShell to determine if it is malicious activity. Review the URL passed to ‘mshta.exe’ to identify if it is from a trusted source., Review the firewall and web proxy logs from this endpoint to identify any malware retrieval from remote systems. Macros run commands using built-in Windows utilities to download malware and compromise the system. These malicious documents leverage macros, which are small Visual Basic for Applications (VBA) scripts embedded inside of Microsoft Office documents, such as Word, PowerPoint, and Excel. ![]()
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