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Detect Certify With PowerShell Script Block Logging

Author
Steven Dick
Source
upstream

The following analytic detects the use of the Certify tool via an in-memory PowerShell function to enumerate Active Directory Certificate Services (AD CS) environments. It leverages PowerShell Script Block Logging (EventCode 4104) to identify specific command patterns associated with Certify's enumeration and exploitation functions. This activity is significant as it indicates potential reconnaissance or exploitation attempts against AD CS, which could lead to unauthorized certificate issuance. If confirmed malicious, attackers could leverage this to escalate privileges, persist in the environment, or access sensitive information by abusing AD CS.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1059.001 Command and Scripting Interpreter: PowerShell
Credential AccessT1649 Steal or Forge Authentication Certificates

Event coverage

ProviderEvent IDTitle
PowerShell4104Creating Scriptblock text (MessageNumber of MessageTotal).

Stages and Predicates

Stage 1: search

search ((ScriptBlockText="* /ca:*" ScriptBlockText IN ("*download *", "*request *")) OR (ScriptBlockText="*find *" ScriptBlockText IN ("* -vulnerable*", "* /enrolleeSuppliesSubject *", "* /json /outfile*", "* /vulnerable*")) OR (ScriptBlockText IN ("* -ca *", "* -u *", "* -username *") ScriptBlockText IN ("*auth *", "*req *"))) EventCode=4104

Stage 2: fillnull

fillnull

Stage 3: stats

stats BY dest, signature, signature_id, user_id, vendor_product, EventID, Guid, Opcode, Name, Path, ProcessID, ScriptBlockId, ScriptBlockText

Stage 4: search

search

Stage 5: search

search

Stage 6: eval

eval ...

Stage 7: eval

eval ... using (command)

Stage 8: 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
EventCodeeq
  • 4104 corpus 108 (splunk 108)
ScriptBlockTextin
  • "* -ca *"
  • "* -u *"
  • "* -username *"
  • "* -vulnerable*"
  • "* /ca:*"
  • "* /enrolleeSuppliesSubject *"
  • "* /json /outfile*"
  • "* /vulnerable*"
  • "*auth *"
  • "*download *"
  • "*find *"
  • "*req *"
  • "*request *"

Neighbors

Broader alternatives (more inclusive than this rule)

These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.