Name:Windows Anomalous Registry Value Length in Environment Key id:f5bde743-245a-4e1f-a152-3971cec6e9ef version:2 date:None author:Teoderick Contreras, Splunk status:production type:Anomaly Description:The following analytic detects creation or modification of registry values under a user or system Environment key (paths matching *\Environment\*) where the stored value exceeds 2,000 characters.
Legitimate environment variables are typically short strings (paths, tokens, or flags); unusually long values can indicate adversaries or malware staging encoded payloads, bloated malicious PATH entries, or other data in a location that is loaded for every interactive session.
This behavior has been observed in contexts such as .NET infostealer activity. Analysts should validate the writing process, value content, and whether the change aligns with trusted software deployment or administrative tasks. Data_source:
-Sysmon EventID 13
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
FROM datamodel=Endpoint.Registry WHERE
Registry.action IN ("created", "modified") Registry.registry_path= "*\\Environment\\*" Registry.registry_value_name != "Path"
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 `Registry` node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product. known_false_positives:No false positives have been identified at this time. References: -https://www.joesandbox.com/analysis/1817558/0/pdfexecutive -https://www.broadcom.com/support/security-center/protection-bulletin/vip-keylogger-spreads-via-multi-org-impersonation-campaign -https://malpedia.caad.fkie.fraunhofer.de/details/win.vipkeylogger drilldown_searches: name:'View the detection results for - "$dest$" and "$user$"' search:'%original_detection_search% | search dest = "$dest$" user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$" and "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$", "$user$") 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:'$info_max_time$' analytic_story:['VIP Keylogger']
