Techniques › T1218.009 › AN1028
AN1028 Analytic 1028
Windows · attack.mitre.org · ATT&CK Enterprise v19.2
<p>Abuse of Regsvcs.exe or Regasm.exe to execute arbitrary code embedded in .NET assemblies via [ComRegisterFunction]/[ComUnregisterFunction]. Behavioral chain: (1) Process creation of regsvcs/regasm with suspicious assembly paths/flags → (2) Assembly/DLL load inside regsvcs/regasm → (3) Registry writes to HKCR\CLSID/ProgID during COM registration → (4) Optional child process or network activity spawned by installer/registration code.</p>
- Detects
- T1218.009 Regsvcs/Regasm
- Part of
- DET0361 Detecting .NET COM Registration Abuse via Regsvcs/Regasm
Log sources and channels
Exactly as MITRE states them in x_mitre_log_source_references. Where a channel is vague, it is vague in the source; kevmap does not tidy it.
| Log source | Channel | Data component |
|---|---|---|
| WinEventLog:Security | EventCode=4688 | DC0032 Process Creation |
| WinEventLog:Sysmon | EventCode=7 | DC0016 Module Load |
| WinEventLog:Sysmon | EventCode=12 | DC0056 Windows Registry Key Creation |
| WinEventLog:Sysmon | EventCode=13, 14 | DC0063 Windows Registry Key Modification |
| WinEventLog:Sysmon | EventCode=11 | DC0039 File Creation |
| WinEventLog:PowerShell | EventCode=4103, 4104, 4105, 4106 | DC0064 Command Execution |
| WinEventLog:Sysmon | EventCode=3, 22 | DC0082 Network Connection Creation |
Mutable elements
Parameters MITRE marks as environment-specific. These are the knobs you are expected to tune; they are why an analytic is not a rule.
| Field | Description |
|---|---|
AssemblyPathRegex | Environment-specific paths to flag (e.g., %TEMP%, Downloads, OneDrive, SMB shares). Helps suppress known-good installers. |
SuspiciousFlags | Arguments like /unregister (/u), /codebase, /regfile which may indicate abuse. Tune per enterprise use of regasm/regsvcs. |
ParentProcessAllowList | Legitimate parents (e.g., setup.exe, msiexec.exe). Analyst can prune false positives from Office or script hosts. |
KnownGoodAssemblies | Hashes or publisher info for approved assemblies commonly registered in the environment. |
RegistryKeyAllowList | Approved CLSIDs/ProgIDs written during sanctioned software installs. |
TimeWindow | Correlation window (e.g., 5–10 min) between file drop → regasm/regsvcs exec → registry writes → child activity. |
SignedToUnsignedTransition | Alert if Microsoft-signed regasm/regsvcs loads or triggers unsigned assemblies/children. |