Detection rules › Splunk

Windows Mimikatz Crypto Export File Extensions

Author
Michael Haag, Splunk
Source
upstream

The following analytic detects the creation of files with extensions commonly associated with the Mimikatz Crypto module. It leverages the Endpoint.Filesystem data model to identify specific file names indicative of certificate export activities. This behavior is significant as it may indicate the use of Mimikatz to export cryptographic keys, which is a common tactic for credential theft. If confirmed malicious, this activity could allow an attacker to exfiltrate sensitive cryptographic material, potentially leading to unauthorized access and further compromise of the environment.

MITRE ATT&CK coverage

TacticTechniques
Credential AccessT1649 Steal or Forge Authentication Certificates

Event coverage

ProviderEvent IDTitle
Sysmon11FileCreate

Stages and Predicates

Stage 1: tstats

tstats WHERE Filesystem.file_name IN ("*.der", "*.keyx.rsa.pvk", "*.pfx", "*dh.ec.p8k", "*dsa.ec.p8k", "*sign.dsa.pvk", "*sign.rsa.pvk") BY Filesystem.action, Filesystem.dest, Filesystem.file_access_time, Filesystem.file_create_time, Filesystem.file_hash, Filesystem.file_modify_time, Filesystem.file_name, Filesystem.file_path, Filesystem.file_acl, Filesystem.file_size, Filesystem.process_guid, Filesystem.process_id, Filesystem.user, Filesystem.vendor_product

Stage 2: search

search

Stage 3: search

search

Stage 4: search

search

Stage 5: search

search `macro`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Filesystem.file_namein
  • "*.der"
  • "*.keyx.rsa.pvk"
  • "*.pfx"
  • "*dh.ec.p8k"
  • "*dsa.ec.p8k"
  • "*sign.dsa.pvk"
  • "*sign.rsa.pvk"