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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: 2022-03-17
  • Author: Teoderick Contreras, Splunk
  • ID: 8776d79c-d26e-11eb-9a56-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1531 Account Access Removal Impact
Kill Chain Phase
  • Exploitation
NIST
  • PR.AC
  • PR.IP
CIS20
  • CIS 4
  • CIS 16
CVE
1
2
3
4
5
6
| from read_ssa_enriched_events() 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), process=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 process IS NOT NULL AND like(process, "%/delete%") AND like(process, "%user%") 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, "process", process, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) 
| into write_ssa_detected_events();

Macros

The SPL above uses the following Macros:

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

Required fields

List of fields required to use this analytic.

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

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.

Known False Positives

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

Associated Analytic Story

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.

:information_source: 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

source | version: 4