Regsvr32StartedByOfficeApplication.md

Detect when Regsvr32.exe is created as subprocess by an Office Application

Query Information

MITRE ATT&CK Technique(s)

Technique ID	Title	Link
T1218.010	System Binary Proxy Execution: Regsvr32	Access https://attack.mitre.org/techniques/T1218/010/

Description

Regsvr32 can be abused to proxy execution of malicious code. It can be spawned from a Office Application to infect the system with malware. The Office applications would not spawn Regsvr32 themselfs.

References

• https://redcanary.com/threat-detection-report/threats/TA551/
• https://threatpost.com/cybercriminals-windows-utility-regsvr32-malware/178333/

Defender XDR

let OfficeApplications = dynamic(['winword.exe', 'powerpnt.exe', 'excel.exe']);
DeviceProcessEvents
| where FileName == "regsvr32.exe"
| where InitiatingProcessFileName has_any (OfficeApplications)
| project
     Timestamp,
     DeviceName,
     AccountName,
     AccountDomain,
     ProcessCommandLine,
     InitiatingProcessCommandLine,
     InitiatingProcessFileName

Sentinel

let OfficeApplications = dynamic(['winword.exe', 'powerpnt.exe', 'excel.exe']);
DeviceProcessEvents
| where FileName == "regsvr32.exe"
| where InitiatingProcessFileName has_any (OfficeApplications)
| project
     TimeGenerated,
     DeviceName,
     AccountName,
     AccountDomain,
     ProcessCommandLine,
     InitiatingProcessCommandLine,
     InitiatingProcessFileName