Encrypting Files with WinRar or 7z

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Identifies use of WinRar or 7z to create an encrypted files. Adversaries will often compress and encrypt data in preparation for exfiltration.

Rule type: eql

Rule indices:

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

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

References:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Collection

Version: 4

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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process where event.type in ("start", "process_started") and
  ((process.name:"rar.exe" or process.code_signature.subject_name == "win.rar GmbH" or
      process.pe.original_file_name == "Command line RAR") and
    process.args == "a" and process.args : ("-hp*", "-p*", "-dw", "-tb", "-ta", "/hp*", "/p*", "/dw", "/tb", "/ta"))

  or
  (process.pe.original_file_name in ("7z.exe", "7za.exe") and
     process.args == "a" and process.args : ("-p*", "-sdel"))

  /* uncomment if noisy for backup software related FPs */
  /* not process.parent.executable : ("C:\\Program Files\\*.exe", "C:\\Program Files (x86)\\*.exe") */

Framework: MITRE ATT&CKTM