Detection rules › Splunk
Certutil De-Obfuscate_Decode Files (Sysmon)
Detects the decoding of PE files inside a certificate (used by MenuPass) - (T1140)
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth |
References
Telemetry coverage
| Provider | Record / event type |
|---|---|
| Sysmon | Event ID 1: Process creation |
Rule body
id: '1031.1036'
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_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
("certutil" (TERM(-decode) OR TERM(-decodehex))) OR (TERM(-decode) OR TERM(-decodehex))
| table _time, host, user event_id, parent_process, parent_process_id, parent_process_name,
parent_process_path, process, process_current_directory, process_hash, process_id,
process_name, process_path, signature_id, user_id | 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:
- Windows Sysmon
references:
- https://www.sentinelone.com/blog/malware-living-off-land-with-certutil/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<") ("certutil" (TERM(-decode) OR TERM(-decodehex))) OR (TERM(-decode) OR TERM(-decodehex))
Stage 2: table
| table _time, host, user event_id, parent_process, parent_process_id, parent_process_name, parent_process_path, process, process_current_directory, process_hash, process_id, process_name, process_path, signature_id, user_id
Stage 3: bucket
| bin span=1s
Stage 4: stats
| stats values(*) as * by _time, host
Stage 5: where
| where match(process, "(?i)-decode")
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
EventCode | eq |
| field:"EventID" kind:eq value:"1" |
process | regex_match |
| field:"CommandLine" kind:regex_match |
Search terms
These SPL tokens match against raw event text.
| Stage | Term |
|---|---|
| 1 | "<EventID>1<" |
| 1 | "certutil" |
| 1 | "-decode" |
| 1 | "-decodehex" |
| 1 | "-decode" |
| 1 | "-decodehex" |