Name:Windows EFI Volume Mount Attempt Via Mountvol id:6ee1d152-56c7-40e8-8db0-edb0074a6bb2 version:2 date:None author:Raven Tait, Splunk status:production type:Anomaly Description:Detects attempts to mount the EFI volume.
The EFI system partition (ESP) is a special partition on a data storage device (usually a hard disk drive or solid-state drive) that computers adhering to the UEFI (Unified Extensible Firmware Interface) specification use to store data necessary for the system to boot, such as bootloaders, device drivers, and system utilities.
This is used with attacks such as PKFail to modify the system on boot. Data_source:
-Sysmon EventID 1
-Windows Event Log Security 4688
-CrowdStrike ProcessRollup2
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
from datamodel=Endpoint.Processes where
( Processes.process_name="mountvol.exe" OR Processes.original_file_name="MOUNTVOL.EXE" ) Processes.process IN ("*-S*", "* /S*")
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:Mounting the EFI volume can be part of normal system updates or legitimate maintenance tasks. Monitor for unusual timing or context to reduce false alerts. References: -https://www.binarly.io/blog/pkfail-untrusted-platform-keys-undermine-secure-boot-on-uefi-ecosystem 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 = "$dest$"' 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:['Compromised Windows Host']
