Name:Windows Symlink Evaluation Change via Fsutil id:9777e7e3-2499-4a16-a519-ebe33630c1e8 version:5 date:None author:Nasreddine Bencherchali, Splunk status:production type:Anomaly Description:This analytic detects the execution of the Windows built-in tool Fsutil.exe with
the "behavior", "set" and "SymlinkEvaluation" parameters.
Attackers can abuse this to alter symlink evaluation behavior on Windows, potentially enabling remote traversal over SMB shares or evading defenses.
Such changes should be uncommon or even rare in enterprise environments and should be investigated.
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="fsutil.exe" OR Processes.original_file_name="fsutil.exe" )
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:Edge cases may exist in environments where this command is used for legitimate purposes.
However, such usage is expected to be uncommon. It is recommended to investigate any occurrences of this command, and apply filters as necessary.
References: -https://learn.microsoft.com/windows-server/administration/windows-commands/fsutil-behavior -https://www.group-ib.com/blog/blackcat/ -https://www.intrinsec.com/alphv-ransomware-gang-analysis/ 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 ("$dest$") | 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:['Windows Post-Exploitation']
