Potential Credential Access via Renamed COM+ Services DLL

Elastic Stack Serverless Security

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 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 (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[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: 1

Rule authors:

• Elastic

Rule license: Elastic License v2

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

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&CKTM

• 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/