splunk-security_content/docs/_posts/2021-11-30-delete_a_net_user.md

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

title	excerpt	categories	last_modified_at	toc	toc_label	tags
Delete A Net User	Account Access Removal	Endpoint	2021-11-30	true		Account Access Removal Impact Splunk Behavioral Analytics Endpoint_Processes

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Description

This analytic will detect a suspicious net.exe/net1.exe command-line to delete a user on a system. This technique may be use by an administrator for legitimate purposes, however this behavior has been used in the wild to impair some user or deleting adversaries tracks created during its lateral movement additional systems. During triage, review parallel processes for additional behavior. Identify any other user accounts created before or after.

• Type: Anomaly
• Product: Splunk Behavioral Analytics
• Datamodel: Endpoint_Processes
• Last Updated: 2021-11-30
• Author: Teoderick Contreras, Splunk
• ID: 8776d79c-d26e-11eb-9a56-acde48001122

ATT&CK

ID	Technique	Tactic
T1531	Account Access Removal	Impact

Search

| from read_ssa_enriched_events() 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), cmd_line=lower(ucast(map_get(input_event, "process"), "string", null)), process_name=lower(ucast(map_get(input_event, "process_name"), "string", null)), process_path=ucast(map_get(input_event, "process_path"), "string", null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) 
| where cmd_line IS NOT NULL AND like(cmd_line, "%/delete%") AND (process_name="net1.exe" OR process_name="net.exe") 
| eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event, "dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"), "string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) 
| into write_ssa_detected_events();

Associated Analytic Story

• XMRig
• Ransomware

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances where renamed net.exe may be used.

Required field

• _time
• dest_device_id
• process_name
• parent_process_name
• process_path
• dest_user_id
• process
• cmd_line

Kill Chain Phase

• Exploitation

Known False Positives

System administrators or scripts may delete user accounts via this technique. Filter as needed.

RBA

Risk Score	Impact	Confidence	Message
49.0	70	70	An instance of parent_process_name spawning process_name was identified on endpoint dest_device_id by user dest_user_id attempting to delete a user account.

Reference

• https://thedfirreport.com/2020/04/20/sqlserver-or-the-miner-in-the-basement/

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/malware/ransomware_ttp/ssa_data1/net_user_del.log
• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1531/atomic_red_team/security.log

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