Linux Stdout Redirection To Dev Null File
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.
Description
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: 2023-04-14
- Author: Teoderick Contreras, Splunk
- ID: de62b809-a04d-46b5-9a15-8298d330f0c8
Annotations
ATT&CK
Kill Chain Phase
- Exploitation
NIST
- DE.AE
CIS20
- CIS 10
CVE
Search
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| 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`
Macros
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.
Required fields
List of fields required to use this analytic.
- _time
- Processes.dest
- Processes.user
- Processes.parent_process_name
- Processes.process_name
- Processes.process
- Processes.process_id
- Processes.parent_process_id
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
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
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.
Reference
- 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
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: 1