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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.*

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: None

Tags:

Elastic
Host
Windows
Threat Detection
Defense Evasion

Version: 6

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?|pptx?|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")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Masquerading
- ID: T1036
- Reference URL: https://attack.mitre.org/techniques/T1036/
Sub-technique:
- Name: Double File Extension
- ID: T1036.007
- Reference URL: https://attack.mitre.org/techniques/T1036/007/
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
Technique:
- Name: User Execution
- ID: T1204
- Reference URL: https://attack.mitre.org/techniques/T1204/
Sub-technique:
- Name: Malicious File
- ID: T1204.002
- Reference URL: https://attack.mitre.org/techniques/T1204/002/

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