CMSTP
The Microsoft Connection Manager Profile Installer (CMSTP.exe) is a command-line program used to install Connection Manager service profiles. (Citation: Microsoft Connection Manager Oct 2009) CMSTP.exe accepts an installation information file (INF) as a parameter and installs a service profile leveraged for remote access connections. Adversaries may supply CMSTP.exe with INF files infected with malicious commands. (Citation: Twitter CMSTP Usage Jan 2018) Similar to Regsvr32 / ”Squiblydoo”, CMSTP.exe may be abused to load and execute DLLs (Citation: MSitPros CMSTP Aug 2017) and/or COM scriptlets (SCT) from remote servers. (Citation: Twitter CMSTP Jan 2018) (Citation: GitHub Ultimate AppLocker Bypass List) (Citation: Endurant CMSTP July 2018) This execution may also bypass AppLocker and other whitelisting defenses since CMSTP.exe is a legitimate, signed Microsoft application. CMSTP.exe can also be abused to Bypass User Account Control and execute arbitrary commands from a malicious INF through an auto-elevated COM interface. (Citation: MSitPros CMSTP Aug 2017) (Citation: GitHub Ultimate AppLocker Bypass List) (Citation: Endurant CMSTP July 2018)
Mitigations |
|
Mitigation | Description |
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CMSTP Mitigation |
CMSTP.exe may not be necessary within a given environment (unless using it for VPN connection installation). Consider using application whitelisting configured to block execution of CMSTP.exe if it is not required for a given system or network to prevent potential misuse by adversaries. (Citation: MSitPros CMSTP Aug 2017) |
Disable or Remove Feature or Program |
Disable or remove unnecessary and potentially vulnerable software, features, or services to reduce the attack surface and prevent abuse by adversaries. This involves identifying software or features that are no longer needed or that could be exploited and ensuring they are either removed or properly disabled. This mitigation can be implemented through the following measures: Remove Legacy Software: - Use Case: Disable or remove older versions of software that no longer receive updates or security patches (e.g., legacy Java, Adobe Flash). - Implementation: A company removes Flash Player from all employee systems after it has reached its end-of-life date. Disable Unused Features: - Use Case: Turn off unnecessary operating system features like SMBv1, Telnet, or RDP if they are not required. - Implementation: Disable SMBv1 in a Windows environment to mitigate vulnerabilities like EternalBlue. Control Applications Installed by Users: - Use Case: Prevent users from installing unauthorized software via group policies or other management tools. - Implementation: Block user installations of unauthorized file-sharing applications (e.g., BitTorrent clients) in an enterprise environment. Remove Unnecessary Services: - Use Case: Identify and disable unnecessary default services running on endpoints, servers, or network devices. - Implementation: Disable unused administrative shares (e.g., C$, ADMIN$) on workstations. Restrict Add-ons and Plugins: - Use Case: Remove or disable browser plugins and add-ons that are not needed for business purposes. - Implementation: Disable Java and ActiveX plugins in web browsers to prevent drive-by attacks. |
Execution Prevention |
Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms. This ensures that only trusted and authorized code is executed, reducing the risk of malware and unauthorized actions. This mitigation can be implemented through the following measures: Application Control: - Use Case: Use tools like AppLocker or Windows Defender Application Control (WDAC) to create whitelists of authorized applications and block unauthorized ones. On Linux, use tools like SELinux or AppArmor to define mandatory access control policies for application execution. - Implementation: Allow only digitally signed or pre-approved applications to execute on servers and endpoints. (e.g., `New-AppLockerPolicy -PolicyType Enforced -FilePath "C:\Policies\AppLocker.xml"`) Script Blocking: - Use Case: Use script control mechanisms to block unauthorized execution of scripts, such as PowerShell or JavaScript. Web Browsers: Use browser extensions or settings to block JavaScript execution from untrusted sources. - Implementation: Configure PowerShell to enforce Constrained Language Mode for non-administrator users. (e.g., `Set-ExecutionPolicy AllSigned`) Executable Blocking: - Use Case: Prevent execution of binaries from suspicious locations, such as `%TEMP%` or `%APPDATA%` directories. - Implementation: Block execution of `.exe`, `.bat`, or `.ps1` files from user-writable directories. Dynamic Analysis Prevention: - Use Case: Use behavior-based execution prevention tools to identify and block malicious activity in real time. - Implemenation: Employ EDR solutions that analyze runtime behavior and block suspicious code execution. |
Detection
Use process monitoring to detect and analyze the execution and arguments of CMSTP.exe. Compare recent invocations of CMSTP.exe with prior history of known good arguments and loaded files to determine anomalous and potentially adversarial activity. Sysmon events can also be used to identify potential abuses of CMSTP.exe. Detection strategy may depend on the specific adversary procedure, but potential rules include: (Citation: Endurant CMSTP July 2018) * To detect loading and execution of local/remote payloads - Event 1 (Process creation) where ParentImage contains CMSTP.exe and/or Event 3 (Network connection) where Image contains CMSTP.exe and DestinationIP is external. * To detect Bypass User Account Control via an auto-elevated COM interface - Event 10 (ProcessAccess) where CallTrace contains CMLUA.dll and/or Event 12 or 13 (RegistryEvent) where TargetObject contains CMMGR32.exe. Also monitor for events, such as the creation of processes (Sysmon Event 1), that involve auto-elevated CMSTP COM interfaces such as CMSTPLUA (3E5FC7F9-9A51-4367-9063-A120244FBEC7) and CMLUAUTIL (3E000D72-A845-4CD9-BD83-80C07C3B881F).
References
- Moe, O. (2017, August 15). Research on CMSTP.exe. Retrieved April 11, 2018.
- Seetharaman, N. (2018, July 7). Detecting CMSTP-Enabled Code Execution and UAC Bypass With Sysmon.. Retrieved August 6, 2018.
- Moe, O. (2018, March 1). Ultimate AppLocker Bypass List. Retrieved April 10, 2018.
- Tyrer, N. (2018, January 30). CMSTP.exe - remote .sct execution applocker bypass. Retrieved April 11, 2018.
- Carr, N. (2018, January 31). Here is some early bad cmstp.exe... Retrieved April 11, 2018.
- Microsoft. (2009, October 8). How Connection Manager Works. Retrieved April 11, 2018.
Связанные риски
Каталоги
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