Name:Windows Suspicious Defender Update Activity in INetCache id:3e25f906-6319-44ad-ab9a-22d162eb3925 version:2 date:None author:Raven Tait, Splunk status:production type:Anomaly Description:Detects a non-Defender process writing mpam-fe*.exe to the Windows Internet Cache (INetCache).
BlueHammer downloads the WD signature update package directly using WinINet as a low-privileged user.
The [1].exe naming suffix is produced by Windows HTTP caching and is a reliable artifact of this download method. Data_source:
-Sysmon EventID 11
-Sysmon EventID 23
search:`sysmon` EventID IN (11, 23, 26) TargetFilename="*\\INetCache*" TargetFilename="*\\mpam-fe[1].exe*" NOT Image IN ( "*:\\Program Files\\Windows Defender*", "*:\\ProgramData\\Microsoft\\Windows Defender*", "*:\\Windows\\System32\\MpSigStub.exe*" ) | fillnull | rename Computer as dest | stats count by dest TargetFilename Image EventID action file_name file_path process_guid process_id user vendor_product | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_suspicious_defender_update_activity_in_inetcache_filter`
how_to_implement:The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process. known_false_positives:Some legitimate system maintenance tools or security scanners may download updates using WinINet and write to INetCache with similar naming patterns. Filter alerts when these tools are verified and approved. References: -https://github.com/Nightmare-Eclipse/BlueHammer drilldown_searches: earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' 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 ("$user$", "$dest$") 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)`' analytic_story:['Windows Persistence Techniques', 'BlueHammer']
