Potential Credential Access via Renamed COM+ Services DLL

Identifies suspicious renamed COMSVCS.DLL Image Load, which exports the MiniDump function that can be used to dump a process memory. This may indicate an attempt to dump Local Security Authority Server Service (LSASS) memory while bypassing command-line based detection in preparation for credential access.

Rule type: eql

Rule indices:

winlogbeat-*
logs-windows.*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://modexp.wordpress.com/2019/08/30/minidumpwritedump-via-com-services-dll/

Tags:

Elastic
Host
Windows
Threat Detection
Credential Access

Version: 3

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

edit

## Config

You will need to enable logging of ImageLoads in your Sysmon configuration to include COMSVCS.DLL by Imphash or Original
File Name.

Rule query

edit

sequence by process.entity_id with maxspan=1m
 [process where event.category == "process" and
    process.name : "rundll32.exe"]
 [process where event.category == "process" and event.dataset : "windows.sysmon_operational" and event.code == "7" and
   (file.pe.original_file_name : "COMSVCS.DLL" or file.pe.imphash : "EADBCCBB324829ACB5F2BBE87E5549A8") and
    /* renamed COMSVCS */
    not file.name : "COMSVCS.DLL"]

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
Technique:
- Name: OS Credential Dumping
- ID: T1003
- Reference URL: https://attack.mitre.org/techniques/T1003/
Sub-technique:
- Name: LSASS Memory
- ID: T1003.001
- Reference URL: https://attack.mitre.org/techniques/T1003/001/

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