Detect Verclsid in Sumo Logic CSE
Adversaries may abuse verclsid.exe to proxy execution of malicious code. Verclsid.exe (Extension CLSID Verification Host) is responsible for verifying each shell extension before it is used by Windows Explorer or the Windows Shell. Adversaries can register a malicious COM object under a CLSID and then invoke verclsid.exe with that CLSID to trigger execution. Since verclsid.exe is signed by Microsoft and performs legitimate COM verification activities, it can bypass application control solutions. Hancitor malware is a known user of this technique.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1218 System Binary Proxy Execution
- Sub-technique
- T1218.012 Verclsid
- Canonical reference
- https://attack.mitre.org/techniques/T1218/012/
Sumo Detection Query
_sourceCategory=*windows*sysmon* EventCode=1
| parse "<Image>*</Image>" as process_image nodrop
| parse "<CommandLine>*</CommandLine>" as command_line nodrop
| parse "<ParentImage>*</ParentImage>" as parent_image nodrop
| parse "<ParentCommandLine>*</ParentCommandLine>" as parent_command_line nodrop
| parse "<User>*</User>" as user nodrop
| parse "<Computer>*</Computer>" as host nodrop
| where toLowerCase(process_image) matches "*\\verclsid.exe" or toLowerCase(parent_image) matches "*\\verclsid.exe"
| eval has_clsid = if(process_image matches "*\\verclsid.exe" and matches(command_line, "\{[0-9A-Fa-f]{8}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{12}\}"), 1, 0)
| eval suspicious_parent = if(matches(toLowerCase(parent_image), "(cmd|powershell|wscript|cscript|mshta|winword|excel|outlook)\.exe"), 1, 0)
| eval forced_exec = if(matches(command_line, "(/s|/c)"), 1, 0)
| eval suspicious_child = if(toLowerCase(parent_image) matches "*\\verclsid.exe" and matches(toLowerCase(process_image), "(cmd|powershell|wscript|cscript)\.exe"), 1, 0)
| eval risk_score = has_clsid + suspicious_parent + forced_exec + suspicious_child
| where risk_score > 1 or suspicious_child = 1
| fields _messageTime, host, user, process_image, command_line, parent_image, parent_command_line, has_clsid, suspicious_parent, forced_exec, suspicious_child, risk_score
| sort by _messageTime descDetects verclsid.exe proxy execution abuse via Sysmon process creation events. Parses key fields from Sysmon XML logs, applies a composite risk scoring model, and surfaces high-risk events where verclsid.exe is launched with CLSID arguments from script interpreters or Office apps, or where verclsid.exe spawns suspicious child processes.
Data Sources
Required Tables
False Positives & Tuning
- Automated software testing frameworks that exercise COM shell extensions and invoke verclsid.exe with specific CLSIDs as part of regression testing
- IT administration scripts (PowerShell or batch) that perform COM class registration verification as part of environment health checks
- Shell extension testing utilities used by developers to validate COM object behavior in Windows Explorer
Other platforms for T1218.012
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Verclsid Execution with CLSID Argument
Expected signal: Sysmon Event ID 1: verclsid.exe with /S /C and CLSID in command line. Security Event ID 4688. The process will attempt to load the COM object registered for this CLSID.
- Test 2Verclsid Launched from cmd.exe
Expected signal: Sysmon Event ID 1: cmd.exe then verclsid.exe with ParentImage=cmd.exe. HasCLSID, ForcedExec, and SuspiciousParent all fire.
- Test 3Malicious COM CLSID Registration for Verclsid Abuse
Expected signal: Sysmon Event ID 13 (Registry Value Set): HKCU\Software\Classes\CLSID path with Temp DLL path as data. The COM registration hunting query captures this as a malicious InprocServer32 pointing to a temp directory.
References (5)
- https://attack.mitre.org/techniques/T1218/012/
- https://lolbas-project.github.io/lolbas/Binaries/Verclsid/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.012/T1218.012.md
- https://www.winosbit.com/articles/what-is-verclsid.exe
- https://www.proofpoint.com/us/threat-insight/post/hancitor-goes-dark
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