Detect Distributed Component Object Model in CrowdStrike LogScale
Adversaries may use Valid Accounts to interact with remote machines by taking advantage of Distributed Component Object Model (DCOM). DCOM extends Windows COM (Component Object Model) beyond local machines using RPC, allowing remote method calls on COM objects. Adversaries with Administrator privileges can remotely obtain code execution through Office applications (Excel, Outlook), MMC20.Application, ShellWindows, and other insecure COM objects. Tools like Empire's Invoke-DCOM, Cobalt Strike, and SILENTTRINITY have built-in DCOM lateral movement capabilities. DCOM communicates over TCP port 135 (RPC endpoint mapper) and dynamically assigned high ports.
MITRE ATT&CK
- Tactic
- Lateral Movement
- Technique
- T1021 Remote Services
- Sub-technique
- T1021.003 Distributed Component Object Model
- Canonical reference
- https://attack.mitre.org/techniques/T1021/003/
LogScale Detection Query
#event_simpleName=ProcessRollup2
| ParentBaseFileName := lower(ParentBaseFileName)
| FileName := lower(FileName)
| dcom_parent := ParentBaseFileName in ("mmc.exe", "excel.exe", "winword.exe", "outlook.exe", "powerpnt.exe", "visio.exe")
| suspicious_child := FileName in ("cmd.exe", "powershell.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe", "regsvr32.exe", "certutil.exe")
| dcom_config_tool := FileName = "dcomcnfg.exe"
| dcom_cmdline := CommandLine = /(?i)DCOM/ AND CommandLine = /(?i)-Exec/
| where dcom_parent AND suspicious_child OR dcom_config_tool OR dcom_cmdline
| DetectionPattern := case {
dcom_config_tool => "DCOM_ConfigTool",
dcom_parent AND suspicious_child => "COM_SuspiciousChild",
dcom_cmdline => "DCOM_CommandLineRef",
* => "DCOM_Other"
}
| table([@timestamp, ComputerName, UserName, FileName, CommandLine, ParentBaseFileName, ParentCommandLine, DetectionPattern])
| sort(@timestamp, order=desc)CrowdStrike LogScale (Falcon SIEM) detection for DCOM lateral movement using ProcessRollup2 telemetry from the Falcon sensor. Normalizes process names to lowercase, evaluates COM host parent/suspicious child combinations, dcomcnfg.exe execution, and DCOM command-line patterns. Outputs a classified detection pattern alongside process context for analyst triage.
Data Sources
Required Tables
False Positives & Tuning
- CrowdStrike Falcon Real Time Response (RTR) sessions where an analyst remotely launches PowerShell or cmd.exe from an Office application context during live incident response
- Patch management tooling (Tanium, BigFix) that uses COM automation via mmc.exe or Office applications to execute remediation scripts on managed endpoints
- Legitimate use of dcomcnfg.exe by system administrators performing DCOM permission hardening or CIS benchmark remediation on Windows Server infrastructure
- Automated testing pipelines on CI/CD build agents running Windows where Excel COM objects are used to validate spreadsheet output and spawn helper scripts
Other platforms for T1021.003
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 1DCOM Lateral Movement via MMC20.Application
Expected signal: Sysmon Event ID 1: powershell.exe process with MMC20.Application in command line. Sysmon Event ID 3: outbound connection to 127.0.0.1 on port 135 and dynamic RPC port. Sysmon Event ID 1 on target: mmc.exe spawning cmd.exe. Sysmon Event ID 11: dcom_test.txt file created in C:\Windows\Temp.
- Test 2DCOM Lateral Movement via ShellWindows
Expected signal: Sysmon Event ID 1: powershell.exe with CLSID 9BA05972 in command line. Sysmon Event ID 3: connection to 127.0.0.1:135. Sysmon Event ID 1: explorer.exe or svchost spawning cmd.exe on the target.
- Test 3Query DCOM Configuration via dcomcnfg
Expected signal: Sysmon Event ID 1: Process Create for dcomcnfg.exe. Security Event ID 4688 (if command-line auditing enabled). The process tree will show dcomcnfg.exe spawning mmc.exe as a child.
References (7)
- https://attack.mitre.org/techniques/T1021/003/
- https://enigma0x3.net/2017/01/05/lateral-movement-using-the-mmc20-application-com-object/
- https://enigma0x3.net/2017/01/23/lateral-movement-via-dcom-round-2/
- https://www.fireeye.com/blog/threat-research/2019/06/hunting-com-objects.html
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1021.003/T1021.003.md
- https://github.com/EmpireProject/Empire/blob/master/data/module_source/lateral_movement/Invoke-DCOM.ps1
- https://learn.microsoft.com/en-us/windows/win32/com/the-component-object-model
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