Detection rules › Splunk
Certutil De-Obfuscate_Decode Files (Windows Event Log)
Detects the decoding of PE files inside a certificate (used by MenuPass) - (T1140)
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth | T1140 Deobfuscate/Decode Files or Information |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
id: '1031.1037'
title: Certutil De-Obfuscate_Decode Files
description: 'Detects the decoding of PE files inside a certificate (used by MenuPass)
- (T1140). -- Threat Actor Association: FIN13, Kimsuky, Revil, TA551, Volt Typhoon
-- Software Association: Astaroth, MINEBRIDGE, Mispadu, VawTrack -- Atomics T1140
Test #1 Atomics T1140 Test #2'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
"<EventID>4688<" OR Type=Process) ("certutil" (TERM(-decode) OR TERM(-decodehex)))
OR (TERM(-decode) OR TERM(-decodehex)) | table _time, host, user event_id, parent_*,
process, process_*, signature_id, src_*, dest_* | bin span=1s | stats values(*)
as * by _time, host | where match(process, "(?i)-decode") '
techniques:
- defense-evasion:deobfuscate/decode files or information
technique_id:
- T1140
data_category:
- Process command-line parameters
- Windows event logs
references:
- https://www.sentinelone.com/blog/malware-living-off-land-with-certutil/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) ("certutil" (TERM(-decode) OR TERM(-decodehex))) OR (TERM(-decode) OR TERM(-decodehex))
Stage 2: table
| table _time, host, user event_id, parent_*, process, process_*, signature_id, src_*, dest_*
Stage 3: bucket
| bin span=1s
Stage 4: stats
| stats values(*) as * by _time, host
Stage 5: where
| where match(process, "(?i)-decode")
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.
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>4688<" |
| 1 | "certutil" |
| 1 | "-decode" |
| 1 | "-decodehex" |
| 1 | "-decode" |
| 1 | "-decodehex" |