Name:Overwriting Accessibility Binaries id:13c2f6c3-10c5-4deb-9ba1-7c4460ebe4ae version:6 date:2024-09-30 author:David Dorsey, Splunk status:production type:TTP Description:The following analytic detects modifications to Windows accessibility binaries such as sethc.exe, utilman.exe, osk.exe, Magnify.exe, Narrator.exe, DisplaySwitch.exe, and AtBroker.exe. It leverages filesystem activity data from the Endpoint.Filesystem data model to identify changes to these specific files. This activity is significant because adversaries can exploit these binaries to gain unauthorized access or execute commands without logging in. If confirmed malicious, this could allow attackers to bypass authentication mechanisms, potentially leading to unauthorized system access and further compromise of the environment. Data_source:
-Sysmon EventID 11
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Filesystem.user) as user values(Filesystem.dest) as dest values(Filesystem.file_path) as file_path from datamodel=Endpoint.Filesystem where (Filesystem.file_path=*\\Windows\\System32\\sethc.exe* OR Filesystem.file_path=*\\Windows\\System32\\utilman.exe* OR Filesystem.file_path=*\\Windows\\System32\\osk.exe* OR Filesystem.file_path=*\\Windows\\System32\\Magnify.exe* OR Filesystem.file_path=*\\Windows\\System32\\Narrator.exe* OR Filesystem.file_path=*\\Windows\\System32\\DisplaySwitch.exe* OR Filesystem.file_path=*\\Windows\\System32\\AtBroker.exe*) by Filesystem.file_name Filesystem.dest | `drop_dm_object_name(Filesystem)` | `security_content_ctime(lastTime)` | `security_content_ctime(firstTime)` | `overwriting_accessibility_binaries_filter`
how_to_implement:You must be ingesting data that records the filesystem activity from your hosts to populate the Endpoint file-system data model node. If you are using Sysmon, you will need a Splunk Universal Forwarder on each endpoint from which you want to collect data. known_false_positives:Microsoft may provide updates to these binaries. Verify that these changes do not correspond with your normal software update cycle. References: drilldown_searches: name:'View the detection results for - "$dest$"' search:'%original_detection_search% | search dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168 | 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:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Data Destruction' - 'Hermetic Wiper' - 'Windows Privilege Escalation' - 'Flax Typhoon' asset_type:Endpoint confidence:90 impact:80 message:A suspicious file modification or replace in $file_path$ in host $dest$ mitre_attack_id: - 'T1546' - 'T1546.008' observable: name:'dest' type:'Hostname' - role: - 'Victim' name:'file_name' type:'File' - role: - 'Attacker' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Filesystem.dest' - 'Filesystem.file_path' - 'Filesystem.file_name' - 'Filesystem.dest' risk_score:72 security_domain:endpoint
