Name:Batch File Write to System32 id:503d17cb-9eab-4cf8-a20e-01d5c6987ae3 version:15 date:None author:Steven Dick, Michael Haag, Rico Valdez, Splunk status:production type:Anomaly Description:The following analytic detects the creation of a batch file (.bat) within the Windows system directory tree, specifically in the System32 or SysWOW64 folders. It leverages data from the Endpoint datamodel, focusing on process and filesystem events to identify this behavior.
This activity is significant because writing batch files to system directories can be indicative of malicious intent, such as persistence mechanisms or system manipulation.
If confirmed malicious, this could allow an attacker to execute arbitrary commands with elevated privileges, potentially compromising the entire system. Data_source:
-Sysmon EventID 11
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
FROM datamodel=Endpoint.Filesystem where
Filesystem.action IN ( "created", "modified" ) Filesystem.file_path IN ( "*:\\Windows\\System32\\*", "*:\\Windows\\SysWOW64\\*" ) Filesystem.file_name IN ( "*.bat", "*.cmd" )
how_to_implement:To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.
You must also be ingesting the Endpoint.Filesystem data source. known_false_positives:Some batch files are written to the system32 directory tree for legitimate purposes, such as system maintenance or configuration. Investigate the batch file to determine if it is legitimate and modify the search to add exclusions, as necessary. References: 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:['SamSam Ransomware', 'Compromised Windows Host']
