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Description

The following analytic identifies hardcoded extensions related to the Crypo module within Mimikatz. Moving certificates or downloading them is not malicious, however with Mimikatz having hardcoded names it helps to identify potential usage of certificates being exported.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2023-02-07
  • Author: Michael Haag, Splunk
  • ID: 3a9a6806-16a8-4cda-8d73-b49d10a05b16

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1649 Steal or Forge Authentication Certificates Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE
1
2
3
4
5
6
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.keyx.rsa.pvk","*sign.rsa.pvk","*sign.dsa.pvk","*dsa.ec.p8k","*dh.ec.p8k", "*.pfx", "*.der") by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `drop_dm_object_name(Filesystem)` 
| `windows_mimikatz_crypto_export_file_extensions_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_mimikatz_crypto_export_file_extensions_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Filesystem.dest
  • Filesystem.file_create_time
  • Filesystem.file_name
  • Filesystem.file_path

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Filesystem node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

False positives may be present and may need to be reviewed before this can be turned into a TTP. In addition, remove .pfx (standalone) if it's too much volume.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
28.0 40 70 Certificate file extensions realted to Mimikatz were identified on disk on $dest$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 1