Name:Linux Kworker Process In Writable Process Path id:1cefb270-74a5-4e27-aa0c-2b6fa7c5b4ed version:4 date:2024-10-17 author:Teoderick Contreras, Splunk status:production type:Hunting Description:The following analytic detects the execution of a kworker process with a command line in writable directories such as /home/, /var/log, and /tmp on a Linux machine. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and parent process paths. This activity is significant as kworker processes are typically kernel threads, and their presence in writable directories is unusual and indicative of potential malware, such as CyclopsBlink. If confirmed malicious, this could allow attackers to blend malicious processes with legitimate ones, leading to persistent access and further system compromise. Data_source:
-Sysmon for Linux EventID 1
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process = "*[kworker/*" Processes.parent_process_path IN ("/home/*", "/tmp/*", "/var/log/*") Processes.process="*iptables*" by Processes.parent_process_name Processes.parent_process Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.parent_process_path Processes.process_guid Processes.dest Processes.user | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `linux_kworker_process_in_writable_process_path_filter`
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 the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. 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 `Processes` 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:unknown References: -https://www.ncsc.gov.uk/files/Cyclops-Blink-Malware-Analysis-Report.pdf -https://www.trendmicro.com/en_us/research/22/c/cyclops-blink-sets-sights-on-asus-routers--.html drilldown_searches:
: tags: analytic_story: - 'Sandworm Tools' - 'Cyclops Blink' asset_type:Endpoint confidence:60 impact:60 message:a $process_name$ with kworker commandline in $dest$ mitre_attack_id: - 'T1036.004' - 'T1036' observable: name:'dest' type:'Hostname' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Processes.dest' - 'Processes.user' - 'Processes.parent_process_name' - 'Processes.process_name' - 'Processes.process' - 'Processes.process_id' - 'Processes.parent_process_id' - 'Processes.parent_process_path' - 'Processes.process_path' risk_score:36 security_domain:endpoint
