Masquerading Space After Filenameedit

This rules identifies a process created from an executable with a space appended to the end of the filename. This may indicate an attempt to masquerade a malicious file as benign to gain user execution. When a space is added to the end of certain files, the OS will execute the file according to it’s true filetype instead of it’s extension. Adversaries can hide a program’s true filetype by changing the extension of the file. They can then add a space to the end of the name so that the OS automatically executes the file when it’s double-clicked.

Rule type: eql

Rule indices:

  • auditbeat-*

Severity: medium

Risk score: 47

Runs every: 5m

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

Maximum alerts per execution: 100



  • Domain: Endpoint
  • OS: Linux
  • OS: macOS
  • Use Case: Threat Detection
  • Tactic: Defense Evasion
  • Data Source: Elastic Defend

Version: 5

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule queryedit

process where host.os.type:("linux","macos") and
  event.type == "start" and
  (process.executable regex~ """/[a-z0-9\s_\-\\./]+\s""") and not in ("ls", "find", "grep", "xkbcomp")