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Description

The following search identifies Eventvwr bypass by identifying the registry modification into a specific path that eventvwr.msc looks to (but is not valid) upon execution. A successful attack will include a suspicious command to be executed upon eventvwr.msc loading. Upon triage, review the parallel processes that have executed. Identify any additional registry modifications on the endpoint that may look suspicious. Remediate as necessary.

  • Type: Anomaly
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint_Registry
  • Last Updated: 2022-02-18
  • Author: Lou Stella, Splunk
  • ID: 66adff66-90d9-11ec-aba7-acde48001122

ATT&CK

ID Technique Tactic
T1548.002 Bypass User Account Control Privilege Escalation, Defense Evasion
T1548 Abuse Elevation Control Mechanism Privilege Escalation, Defense Evasion
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| from read_ssa_enriched_events() 
| where "Endpoint_Registry" IN (_datamodels) 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), registry_path=lower(ucast(map_get(input_event, "registry_path"), "string", null)), registry_hive=lower(ucast(map_get(input_event, "registry_hive"), "string", null)), registry_value_name=lower(ucast(map_get(input_event, "registry_value_name"), "string", null)), registry_key_name=lower(ucast(map_get(input_event, "parent_process_name"), "string", null)), registry_value_type=lower(ucast(map_get(input_event, "registry_value_type"), "string", null)), registry_value_data=lower(ucast(map_get(input_event, "registry_value_data"), "string", null)), process_guid=lower(ucast(map_get(input_event, "process_guid"), "string", null)) 
| where registry_path IS NOT NULL AND (like (registry_path, "%mscfile\\\\shell\\\\open\\\\command%")) 
| 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)) 
| eval body=create_map(["registry_path", registry_path, "registry_hive", registry_hive, "registry_value_name", registry_value_name, "registry_key_name", registry_key_name, "registry_value_type", registry_value_type, "registry_value_data", registry_value_data, "process_guid", process_guid]) 
| into write_ssa_detected_events();

Macros

The SPL above uses the following Macros:

Note that windows_eventvwr_uac_bypass_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
  • event_id
  • registry_path
  • registry_hive
  • registry_value_name
  • registry_key_name
  • registry_value_type
  • registry_value_data
  • process_guid

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_Registry datamodel.

Known False Positives

None known at this time.

Associated Analytic story

Kill Chain Phase

  • Privilege Escalation

RBA

Risk Score Impact Confidence Message
80.0 80 100 Registry values were modified to bypass UAC using Event Viewer on $dest_device_id$

Note that risk score is calculated base on the following formula: (Impact * Confidence)/100

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

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