Detection: Linux Auditd Preload Hijack Library Calls

Description

The following analytic detects the use of the LD_PRELOAD environment variable to hijack or hook library functions on a Linux platform. It leverages data from Linux Auditd, focusing on process execution logs that include command-line details. This activity is significant because adversaries, malware authors, and red teamers commonly use this technique to gain elevated privileges and establish persistence on a compromised machine. If confirmed malicious, this behavior could allow attackers to execute arbitrary code, escalate privileges, and maintain long-term access to the system.

Search

1`linux_auditd` `linux_auditd_normalized_execve_process` 
2| rename host as dest 
3| rename comm as process_name 
4| rename exe as process 
5| where LIKE (process_exec, "%LD_PRELOAD%")
6| stats count min(_time) as firstTime max(_time) as lastTime by argc process_exec dest 
7| `security_content_ctime(firstTime)`
8| `security_content_ctime(lastTime)`
9| `linux_auditd_preload_hijack_library_calls_filter`

Data Source

Name	Platform	Sourcetype	Source
Linux Auditd Execve	Linux	'linux:audit'	'/var/log/audit/audit.log'

Macros Used

Annotations

Default Configuration

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

Implementation

To implement this detection, the process begins by ingesting auditd data, that consists of SYSCALL, TYPE, EXECVE and PROCTITLE events, which captures command-line executions and process details on Unix/Linux systems. These logs should be ingested and processed using Splunk Add-on for Unix and Linux (https://splunkbase.splunk.com/app/833), which is essential for correctly parsing and categorizing the data. The next step involves normalizing the field names to match the field names set by the Splunk Common Information Model (CIM) to ensure consistency across different data sources and enhance the efficiency of data modeling. This approach enables effective monitoring and detection of linux endpoints where auditd is deployed

Known False Positives

Administrator or network operator can execute this command. Please update the filter macros to remove false positives.

Associated Analytic Story

• Compromised Linux Host

• Earth Estries

• Linux Persistence Techniques

• Linux Privilege Escalation

• Nexus APT Threat Activity

Risk Based Analytics (RBA)

Risk Message:

A [$process_exec$] event occurred on host - [$dest$] to hijack or hook library functions using the LD_PRELOAD environment variable.

References

• https://compilepeace.medium.com/memory-malware-part-0x2-writing-userland-rootkits-via-ld-preload-30121c8343d5

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: 4