Detectionhightest
File In Suspicious Location Encoded To Base64 Via Certutil.EXE
Detects the execution of certutil with the "encode" flag to encode a file to base64 where the files are located in potentially suspicious locations
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Nasreddine Bencherchali (Nextron Systems)Created Mon May 15Updated Tue Mar 0582a6714f-4899-4f16-9c1e-9a333544d4c3windows
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 Logic3 selectors
detection:
selection_img:
- Image|endswith: '\certutil.exe'
- OriginalFileName: 'CertUtil.exe'
selection_cli:
CommandLine|contains|windash: '-encode'
selection_extension:
CommandLine|contains:
# Note: Add more suspicious locations to increase coverage
- '\AppData\Roaming\'
- '\Desktop\'
- '\Local\Temp\'
- '\PerfLogs\'
- '\Users\Public\'
- '\Windows\Temp\'
- '$Recycle.Bin'
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
82a6714f-4899-4f16-9c1e-9a333544d4c3
Status
test
Level
high
Type
Detection
Created
Mon May 15
Modified
Tue Mar 05
Path
rules/windows/process_creation/proc_creation_win_certutil_encode_susp_location.yml
Raw Tags
attack.defense-evasionattack.t1027