Detectionhightest
File Decoded From Base64/Hex Via Certutil.EXE
Detects the execution of certutil with either the "decode" or "decodehex" flags to decode base64 or hex encoded files. This can be abused by attackers to decode an encoded payload before execution
Convert In Phoenix Studio
Open this Sigma rule in the converter with the YAML preloaded and ready for backend selection.
Launch
Florian Roth (Nextron Systems), Jonhnathan Ribeiro, oscd.communityCreated Wed Feb 15Updated Wed Jun 04cc9cbe82-7bc0-4ef5-bc23-bbfb83947be7windows
Log Source
WindowsProcess Creation
ProductWindows← raw: windows
CategoryProcess Creation← raw: process_creation
Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.
Detection Logic
Detection Logic2 selectors
detection:
selection_img:
- Image|endswith: '\certutil.exe'
- OriginalFileName: 'CertUtil.exe'
selection_cli:
CommandLine|contains|windash:
- '-decode ' # Decode Base64
- '-decodehex ' # Decode Hex
condition: all of selection_*False Positives
Unknown
False positive likelihood has not been assessed. Additional context may be needed during triage.
References
MITRE ATT&CK
Tactics
Techniques
Rule Metadata
Rule ID
cc9cbe82-7bc0-4ef5-bc23-bbfb83947be7
Status
test
Level
high
Type
Detection
Created
Wed Feb 15
Modified
Wed Jun 04
Path
rules/windows/process_creation/proc_creation_win_certutil_decode.yml
Raw Tags
attack.defense-evasionattack.t1027