Executable File Creation with Multiple Extensions

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Executable File Creation with Multiple Extensions

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Masquerading can allow an adversary to evade defenses and better blend in with the environment. One way it occurs is when the name or location of a file is manipulated as a means of tricking a user into executing what they think is a benign file type but is actually executable code.

Rule type: eql

Rule indices:

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

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

Tags:

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

Version: 101 (version history)

Added (Elastic Stack release): 7.12.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guide

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Rule query

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file where event.type == "creation" and file.extension : "exe" and
file.name regex~ """.*\.(vbs|vbe|bat|js|cmd|wsh|ps1|pdf|docx?|xlsx?|pp
tx?|txt|rtf|gif|jpg|png|bmp|hta|txt|img|iso)\.exe""" and not
(process.executable : ("?:\\Windows\\System32\\msiexec.exe",
"C:\\Users\\*\\QGIS_SCCM\\Files\\QGIS-OSGeo4W-*-Setup-x86_64.exe") and
file.path : "?:\\Program Files\\QGIS *\\apps\\grass\\*.exe") and not
process.executable : ("/bin/sh", "/usr/sbin/MailScanner",
"/usr/bin/perl")

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 101 (8.6.0 release)
  • Formatting only
Version 100 (8.5.0 release)
  • Formatting only
Version 6 (8.4.0 release)
  • Updated query, changed from:

    file where event.type == "creation" and file.extension : "exe" and
    file.name regex~ """.*\.(vbs|vbe|bat|js|cmd|wsh|ps1|pdf|docx?|xlsx?|pp
    tx?|txt|rtf|gif|jpg|png|bmp|hta|txt|img|iso)\.exe"""
Version 4 (8.2.0 release)
  • Formatting only
Version 3 (7.16.0 release)
  • Formatting only
Version 2 (7.14.0 release)
  • Updated query, changed from:

    file where event.type == "creation" and file.extension:"exe" and
    file.name: ( "*.vbs.exe", "*.vbe.exe", "*.bat.exe",
    "*.js.exe", "*.cmd.exe", "*.wsh.exe", "*.ps1.exe",
    "*.pdf.exe", "*.docx.exe", "*.doc.exe", "*.xlsx.exe",
    "*.xls.exe", "*.pptx.exe", "*.ppt.exe", "*.txt.exe",
    "*.rtf.exe", "*.gif.exe", "*.jpg.exe", "*.png.exe",
    "*.bmp.exe", "*.hta.exe", "*.txt.exe", "*.img.exe",
    "*.iso.exe" )