THIS IS A EXPERIMENTAL DETECTION
This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.
This analytic looks for suspicious commandline that redirect the stdout or possible stderror to dev/null file. This technique was seen in cyclopsblink malware where it redirect the possible output or error while modify the iptables firewall setting of the compromised machine to hide its action from the user. This Anomaly detection is a good pivot to look further why process or user use this un common approach.
- Type: Anomaly
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2022-04-05
- Author: Teoderick Contreras, Splunk
- ID: de62b809-a04d-46b5-9a15-8298d330f0c8
Kill Chain Phase
- CIS 3
- CIS 5
- CIS 16
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.process = "*&>/dev/null*" by Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.process_guid Processes.dest Processes.user Processes.parent_process_name | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `linux_stdout_redirection_to_dev_null_file_filter`
The SPL above uses the following Macros:
linux_stdout_redirection_to_dev_null_file_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
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
Associated Analytic Story
|36.0||60||60||a commandline $process$ that redirect stdout to dev/null in $dest$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1