CAR-2021-05-002.yml

title: Batch File Write to System32
submission_date: 2021/05/11
information_domain: Analytic
platforms:
- Windows
subtypes:
- Process
analytic_types:
- TTP
contributors:
- Splunk Threat Research <research@splunk.com>
id: CAR-2021-05-002
description: While batch files are not inherently malicious, it is uncommon to see them created after OS installation, especially in the Windows directory. This analytic looks for the suspicious activity of a batch file being created within the C:\Windows\System32 directory tree. There will be only occasional false positives due to administrator actions.
coverage:
- technique: T1204.002
  tactics:
  - TA0002
  coverage: Moderate
implementations:
-	name: Pseudocode – Batch file created in the Windows system32 directory tree
  description: Pseudocode implementation of the Splunk search below
  code: |- 
      files = search File:create
      batch_files = filter files where (
        extension =".bat" AND file_path = "C:\Windows\system32*" )
      output batch_files
  data_model: CAR native
  type: Pseudocode
- name: Splunk code
  description: You must be ingesting data that records the file-system activity from
    your hosts to populate the Endpoint file-system data-model node. If you are using
    Sysmon, you will need a Splunk Universal Forwarder on each endpoint from which
    you want to collect data.
  code: '| tstats count min(_time) as firstTime max(_time) as lastTime values(Filesystem.dest)
    as dest values(Filesystem.file_name) as file_name values(Filesystem.user) as user
    from datamodel=Endpoint.Filesystem by Filesystem.file_path   | rex field=file_name
    "(?<file_extension>\.[^\.]+)$" | search file_path=*system32* AND file_extension=.bat'
  type: Splunk
  data_model: Endpoint

unit_tests:
- configurations:
  - Using Splunk [Attack Range](https://github.com/splunk/attack_range)
  description: Replay the detection [dataset](https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1204.002/batch_file_in_system32/windows-sysmon.log)  using
    the Splunk attack range with the commands below
  commands:
  - python attack_range.py replay -dn data_dump [--dump NAME_OF_DUMP]
- configurations:
  - Using [Invoke-AtomicRedTeam](https://github.com/redcanaryco/invoke-atomicredteam)
  description: execute the atomic test [T1204.002](https://github.com/redcanaryco/atomic-red-team/tree/master/atomics/T1204.002)
    against a Windows target.
  commands:
  - Invoke-AtomicTest T1204.002