Name:Ransomware Notes bulk creation id:eff7919a-8330-11eb-83f8-acde48001122 version:9 date:2025-05-02 author:Teoderick Contreras, Splunk 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 values(action) as action values(file_access_time) as file_access_time values(file_create_time) as file_create_time values(file_hash) as file_hash values(file_modify_time) as file_modify_time values(file_path) as file_path values(file_acl) as file_acl values(file_size) as file_size values(process_guid) as process_guid values(process_id) as process_id values(user) as user values(vendor_product) as vendor_product by dest file_name | 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: - 'BlackMatter Ransomware' - 'DarkSide Ransomware' - 'Chaos Ransomware' - 'Rhysida Ransomware' - 'LockBit Ransomware' - 'Medusa Ransomware' - 'Black Basta Ransomware' - 'Clop Ransomware' - 'Cactus Ransomware' - 'Termite Ransomware' asset_type:Endpoint mitre_attack_id: - 'T1486' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' security_domain:endpoint
