splunk-security_content/docs/_posts/2021-09-16-batch_file_write_to_system32.md

title, excerpt, categories, last_modified_at, toc, toc_label, tags

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Batch File Write to System32	User Execution , Malicious File	Endpoint	2021-09-16	true		User Execution Malicious File Execution Execution Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

The search looks for a batch file (.bat) written to the Windows system directory tree.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint- Datasource: Splunk Add-on for Sysmon
• Last Updated: 2021-09-16
• Author: Michael Haag, Rico Valdez, Splunk
• ID: 503d17cb-9eab-4cf8-a20e-01d5c6987ae3

Annotations

ATT&CK

ID	Technique	Tactic
T1204	User Execution	Execution

| T1204.002 | Malicious File | Execution |

Kill Chain Phase

• Delivery

NIST

• PR.PT
• DE.CM

CIS20

• CIS 8

CVE

Search

| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name=*  by _time span=1h Processes.process_id Processes.process_name Processes.dest 
| `drop_dm_object_name(Processes)` 
| join process_guid, _time [
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\system32\\*", "*\\syswow64\\*") Filesystem.file_name="*.bat" by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path 
| `drop_dm_object_name(Filesystem)` 
| fields _time dest file_create_time file_name file_path process_name process_path process] 
| dedup file_create_time 
| table dest file_create_time, file_name, file_path, process_name  
| `batch_file_write_to_system32_filter`

Macros

The SPL above uses the following Macros:

• security_content_summariesonly

ℹ️ batch_file_write_to_system32_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

• _time
• Filesystem.dest
• Filesystem.file_name
• Filesystem.user
• Filesystem.file_path
• Processes.process_id
• Processes.process_name
• Processes.dest

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

It is possible for this search to generate a notable event for a batch file write to a path that includes the string "system32", but is not the actual Windows system directory. As such, you should confirm the path of the batch file identified by the search. In addition, a false positive may be generated by an administrator copying a legitimate batch file in this directory tree. You should confirm that the activity is legitimate and modify the search to add exclusions, as necessary.

Associated Analytic story

• SamSam Ransomware

RBA

Risk Score	Impact	Confidence	Message
63.0	70	90	A file - file_name was written to system32 has occurred on endpoint dest by user user.

ℹ️ The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1204.002/batch_file_in_system32/windows-sysmon.log

source | version: 2