Whitespace Padding in Process Command Line

Elastic Stack Serverless Security

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:

• winlogbeat-*
• logs-endpoint.events.*
• logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://twitter.com/JohnLaTwC/status/1419251082736201737

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Defense Evasion

Version: 2

Rule authors:

• Elastic

Rule license: Elastic License v2

• 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,}.*"

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Defense Evasion
  • ID: TA0005
  • Reference URL: https://attack.mitre.org/tactics/TA0005/