Detection rules › Splunk
Certutil Obfuscate_Encode Files (PowerShell)
Certutil can be used to encode files to evade defensive measures
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth | |
| Command & Control |
References
Telemetry coverage
Rule body
id: '6158.6686'
title: Certutil Obfuscate_Encode Files
description: 'Certutil can be used to encode files to evade defensive measures. --
Threat Actor Association: APT29/Nobelium/Cozy Bear, Arid Viper/APT C-23, BlackTech
- Software Association: Conti'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_powershell` (TERM(EventCode=4104) OR
"<EventID>4104<" OR TERM(EventCode=4103) OR "<EventID>4103<") "certutil" TERM(encode)
| table _time, host, user, signature_id, process | bin span=1s | stats values(*)
as * by _time, host '
techniques:
- command-and-control:data encoding
- defense-evasion:obfuscated files or information
technique_id:
- T1027
- T1132
data_category:
- PowerShell logs
- Process command-line parameters
references:
- https://lolbas-project.github.io/lolbas/Binaries/Certutil/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_powershell` (TERM(EventCode=4104) OR "<EventID>4104<" OR TERM(EventCode=4103) OR "<EventID>4103<") "certutil" TERM(encode)
Stage 2: table
| table _time, host, user, signature_id, process
Stage 3: bucket
| bin span=1s
Stage 4: stats
| stats values(*) as * by _time, host
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
EventCode | eq |
| field:"EventID" kind:eq |
Search terms
These SPL tokens match against raw event text.
| Stage | Term |
|---|---|
| 1 | "<EventID>4104<" |
| 1 | "<EventID>4103<" |
| 1 | "certutil" |
| 1 | encode |