Name:Linux Possible Ssh Key File Creation id:c04ef40c-72da-11ec-8eac-acde48001122 version:3 date:2024-09-30 author:Teoderick Contreras, Splunk status:production type:Anomaly Description:The following analytic detects the creation of SSH key files in the ~/.ssh/ directory. It leverages filesystem data to identify new files in this specific path. This activity is significant because threat actors often create SSH keys to gain persistent access and escalate privileges on a compromised host. If confirmed malicious, this could allow attackers to remotely access the machine using the OpenSSH daemon service, leading to potential unauthorized control and data exfiltration. 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 IN ("*/.ssh*") by Filesystem.dest Filesystem.file_name Filesystem.process_guid Filesystem.file_path | `drop_dm_object_name(Filesystem)` | `security_content_ctime(lastTime)` | `security_content_ctime(firstTime)` | `linux_possible_ssh_key_file_creation_filter`
how_to_implement:To successfully implement this search, you need to be ingesting logs with the file name, file path, and process_guid executions from your endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from Splunkbase. known_false_positives:Administrator or network operator can create file in ~/.ssh folders for automation purposes. Please update the filter macros to remove false positives. References: -https://www.hackingarticles.in/ssh-penetration-testing-port-22/ -https://attack.mitre.org/techniques/T1098/004/ 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: - 'Linux Privilege Escalation' - 'Linux Persistence Techniques' - 'Linux Living Off The Land' asset_type:Endpoint confidence:60 impact:60 message:A file $file_name$ is created in $file_path$ on $dest$ mitre_attack_id: - 'T1098.004' - 'T1098' observable: name:'dest' type:'Hostname' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Filesystem.dest' - 'Filesystem.file_create_time' - 'Filesystem.file_name' - 'Filesystem.process_guid' - 'Filesystem.file_path' risk_score:36 security_domain:endpoint
