Name:Hide User Account From Sign-In Screen id:834ba832-ad89-11eb-937d-acde48001122 version:16 date:None author:Teoderick Contreras, Splunk, Steven Dick status:production type:TTP Description:The following analytic detects a suspicious registry modification that hides a user account from the Windows Login screen. It leverages data from the Endpoint.Registry data model, specifically monitoring changes to the registry path "*\\Windows NT\\CurrentVersion\\Winlogon\\SpecialAccounts\\Userlist*" with a value of "0x00000000". This activity is significant as it may indicate an adversary attempting to create a hidden admin account to avoid detection and maintain persistence on the compromised machine. If confirmed malicious, this could allow the attacker to maintain undetected access and control over the system, posing a severe security risk. Data_source:
-Sysmon EventID 13
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path="*\\Windows NT\\CurrentVersion\\Winlogon\\SpecialAccounts\\Userlist*" AND Registry.registry_value_data = "0x00000000") by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive Registry.registry_path Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product | `drop_dm_object_name(Registry)` | where isnotnull(registry_value_data) | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `hide_user_account_from_sign_in_screen_filter`
how_to_implement:To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the official Sysmon TA. https://splunkbase.splunk.com/app/5709 known_false_positives:No false positives have been identified at this time. References: -https://thedfirreport.com/2020/04/20/sqlserver-or-the-miner-in-the-basement/ drilldown_searches: name:'View the detection results for - "$user$" and "$dest$"' search:'%original_detection_search% | search user = "$user$" dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$" and "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'7d' latest_offset:'0' analytic_story:['XMRig', 'Windows Registry Abuse', 'Azorult', 'Warzone RAT']
