⚠️ WARNING THIS IS A EXPERIMENTAL DETECTION

We have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.

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Description

This analytic is built to detect a suspicious modification of the Windows registry related to UAC bypass. This technique is to modify the registry in this detection, create a registry value with the path of the payload and run WSreset.exe to bypass User Account Control.

  • Type: Anomaly
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint_Registry
  • Last Updated: 2022-02-18
  • Author: Lou Stella, Splunk
  • ID: 3118f0c2-90d9-11ec-b833-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, "registry_key_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 registry_value_name IS NOT NULL and like (registry_path, "%\\\\AppX82a6gwre4fdg3bt635tn5ctqjf8msdd2\\\\Shell\\\\open\\\\command%") AND (registry_value_name="(Default)" OR registry_value_name="DelegateExecute") 
| 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_wsreset_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
  • 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

Unknown at this point in time.

Associated Analytic story

Kill Chain Phase

  • Privilege Escalation

RBA

Risk Score Impact Confidence Message
63.0 70 90 None

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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