CMSTP

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CMSTP
Technique
ID T1191
Tactic Defense Evasion, Execution
Platform Windows
Permissions Required User
Data Sources Process Monitoring, Process command-line parameters
Supports Remote No
Defense Bypassed Application whitelisting, Anti-virus
Contributors Ye Yint Min Thu Htut, Offensive Security Team, DBS Bank

The Microsoft Connection Manager Profile Installer (CMSTP.exe) is a command-line program used to install Connection Manager service profiles.1 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.2 Similar to Regsvr32 / ”Squiblydoo”, CMSTP.exe may be abused to load and execute DLLs3 and/or COM scriptlets (SCT) from remote servers.45 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.35

Examples

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.3

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.