Detection: Linux GNU Awk Privilege Escalation

Description

The following analytic detects the execution of the 'gawk' command with elevated privileges on a Linux system. It leverages Endpoint Detection and Response (EDR) telemetry to identify command-line executions where 'gawk' is used with 'sudo' and 'BEGIN{system' patterns. This activity is significant because it indicates a potential privilege escalation attempt, allowing a user to execute system commands as root. If confirmed malicious, this could lead to full root access, enabling the attacker to control the system, modify critical files, and maintain persistent access.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process="*gawk*" AND Processes.process="*BEGIN*{system*" AND Processes.process="*sudo*" by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `linux_gnu_awk_privilege_escalation_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon for Linux EventID 1	Linux	'sysmon:linux'	'Syslog:Linux-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

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

False positives may be present, filter as needed.

Associated Analytic Story

• Linux Living Off The Land

• Linux Privilege Escalation

Risk Based Analytics (RBA)

Risk Message:

An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$

References

• https://gtfobins.github.io/gtfobins/gawk/

• https://www.geeksforgeeks.org/gawk-command-in-linux-with-examples/

Detection Testing

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: GitHub | Version: 9