Detection rules › Sigma
Suspicious Filename with Embedded Base64 Commands
Detects files with specially crafted filenames that embed Base64-encoded bash payloads designed to execute when processed by shell scripts. These filenames exploit shell interpretation quirks to trigger hidden commands, a technique observed in VShell malware campaigns.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Execution | T1059.004 Command and Scripting Interpreter: Unix Shell |
| Stealth | T1027 Obfuscated Files or Information |
Event coverage
| Provider | Event |
|---|---|
| Sysmon-for-Linux | Event ID 11 |
Rule body yaml
title: Suspicious Filename with Embedded Base64 Commands
id: 179b3686-6271-4d87-807d-17d843a8af73
status: experimental
description: |
Detects files with specially crafted filenames that embed Base64-encoded bash payloads designed to execute when processed by shell scripts.
These filenames exploit shell interpretation quirks to trigger hidden commands, a technique observed in VShell malware campaigns.
references:
- https://www.trellix.com/blogs/research/the-silent-fileless-threat-of-vshell/
author: '@kostastsale'
date: 2025-11-22
tags:
- attack.execution
- attack.stealth
- attack.t1059.004
- attack.t1027
logsource:
product: linux
category: file_event
detection:
selection:
TargetFilename|contains:
- '{echo'
- '{base64,-d}'
condition: selection
falsepositives:
- Legitimate files with similar naming patterns (very unlikely).
level: high
Stages and Predicates
Stage 0: condition
selectionStage 1: selection
selection:
TargetFilename|contains:
- '{echo'
- '{base64,-d}'
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.
| Field | Kind | Values |
|---|---|---|
TargetFilename | match |
|