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Description

This analytic looks for suspicious process kworker commandline in a linux machine. kworker process name or thread are common names of kernel threads in linux process. This hunting detections can lead to investigate process contains process path in writable directory in linux like /home/, /var/log and /tmp/. This technique was seen in cyclopsblink malware to blend its core and other of its child process as normal kworker on the compromised machine. This detection might be a good pivot to look for other IOC related to cyclopsblink malware or attacks.

  • Type: Hunting
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-04-30
  • Author: Teoderick Contreras, Splunk
  • ID: 1cefb270-74a5-4e27-aa0c-2b6fa7c5b4ed

Annotations

ATT&CK
ID Technique Tactic
T1036.004 Masquerade Task or Service Defense Evasion
T1036 Masquerading Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE
1
2
3
4
5
6
| 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`

Macros

The SPL above uses the following Macros:

Note that linux_kworker_process_in_writable_process_path_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _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

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from Splunkbase.

Known False Positives

unknown

Associated Analytic story

RBA

Risk Score Impact Confidence Message
36.0 60 60 a $process_name$ with kworker commandline in $dest$

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 2