Whitespace Padding in Process Command Line

Identifies process execution events where the command line value contains a long sequence of whitespace characters or multiple occurrences of contiguous whitespace. Attackers may attempt to evade signature-based detections by padding their malicious command with unnecessary whitespace characters. These observations should be investigated for malicious behavior.

Rule type: eql

Rule indices:

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Version: 2 (version history)

Added (Elastic Stack release): 7.15.0

Last modified (Elastic Stack release): 7.16.0

Rule authors: Elastic

Rule license: Elastic License v2

## Triage and analysis

- Analyze the command line of the process in question for evidence of malicious code execution.
- Review the ancestor and child processes spawned by the process in question for indicators of further malicious code execution.

process where event.type in ("start", "process_started") and
process.command_line regex ".*[ ]{20,}.*" or /* this will match
on 3 or more separate occurrences of 5+ contiguous whitespace
characters */ process.command_line regex ".*(.*[ ]{5,}[^ ]*){3,}.*"