Name:Linux MOTD Script Added id:6dd14256-559b-4364-99d8-0968407b8074 version:1 date:None author:Raven Tait, Splunk status:production type:Anomaly Description:The following analytic detects the creation of a file within the /etc/update-motd.d directory.
This is used to add scripts that run with Message of the Day (MOTD) when a user logs in.
This can be used by attackers for persistence if it contains malicious code. Data_source:
-Sysmon for Linux EventID 11
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
from datamodel=Endpoint.Filesystem where
Filesystem.file_path="/etc/update-motd.d/*" Filesystem.action IN ("created", "modified")
by Filesystem.file_path Filesystem.file_name Filesystem.user Filesystem.dest Filesystem.action Filesystem.process_guid Filesystem.process_id
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 file creation events including the file path and user context. 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 `Filesystem` 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:Legitimate system administrators may add or modify MOTD scripts for valid operational purposes such as displaying system information or login banners. Filter based on known administrative activity and authorized users. References: -https://github.com/Aegrah/PANIX 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:['Linux Persistence Techniques', 'Linux Post-Exploitation']
