Name:Ransomware Notes bulk creation id:eff7919a-8330-11eb-83f8-acde48001122 version:3 date:2024-09-30 author:Teoderick Contreras status:production type:Anomaly Description:The following analytic identifies the bulk creation of ransomware notes (e.g., .txt, .html, .hta files) on an infected machine. It leverages Sysmon EventCode 11 to detect multiple instances of these file types being created within a short time frame. This activity is significant as it often indicates an active ransomware attack, where the attacker is notifying the victim of the encryption. If confirmed malicious, this behavior could lead to widespread data encryption, rendering critical files inaccessible and potentially causing significant operational disruption. Data_source:
-Sysmon EventID 11
search:`sysmon` EventCode=11 file_name IN ("*\.txt","*\.html","*\.hta") |bin _time span=10s | stats min(_time) as firstTime max(_time) as lastTime dc(TargetFilename) as unique_readme_path_count values(TargetFilename) as list_of_readme_path by Computer Image file_name | rename Computer as dest | where unique_readme_path_count >= 15 | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `ransomware_notes_bulk_creation_filter`
how_to_implement:You must be ingesting data that records the filesystem activity from your hosts to populate the Endpoint file-system data model node. If you are using Sysmon, you will need a Splunk Universal Forwarder on each endpoint from which you want to collect data. known_false_positives:unknown References: -https://www.mandiant.com/resources/fin11-email-campaigns-precursor-for-ransomware-data-theft -https://blog.virustotal.com/2020/11/keep-your-friends-close-keep-ransomware.html 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 ("$dest$") 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:'$info_max_time$' tags: analytic_story: - 'Clop Ransomware' - 'DarkSide Ransomware' - 'BlackMatter Ransomware' - 'Chaos Ransomware' - 'LockBit Ransomware' - 'Rhysida Ransomware' asset_type:Endpoint confidence:90 impact:90 message:A high frequency file creation of $file_name$ in different file path in host $dest$ mitre_attack_id: - 'T1486' observable: name:'dest' type:'Hostname' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - 'EventCode' - 'file_name' - '_time' - 'TargetFilename' - 'dest' - 'Image' - 'user' risk_score:81 security_domain:endpoint
