Detection: Windows DLL Search Order Hijacking Hunt with Sysmon

Updated Date: 2025-02-10 ID: 79c7d1fc-64c7-91be-a616-ccda752efe81 Author: Michael Haag, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic identifies potential DLL search order hijacking or DLL sideloading by detecting known Windows libraries loaded from non-standard directories. It leverages Sysmon EventCode 7 to monitor DLL loads and cross-references them with a lookup of known hijackable libraries. This activity is significant as it may indicate an attempt to execute malicious code by exploiting DLL search order vulnerabilities. If confirmed malicious, this could allow attackers to gain code execution, escalate privileges, or maintain persistence within the environment.

Search

1`sysmon` EventCode=7 NOT (process_path IN ("*\\system32\\*", "*\\syswow64\\*","*\\winsxs\\*","*\\wbem\\*")) 
2| lookup hijacklibs library AS loaded_file OUTPUT islibrary 
3| search islibrary = True 
4| stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded dest loaded_file loaded_file_path original_file_name process_exec process_guid process_hash process_id process_name process_path service_dll_signature_exists service_dll_signature_verified signature signature_id user_id vendor_product 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `windows_dll_search_order_hijacking_hunt_with_sysmon_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 7	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_dll_search_order_hijacking_hunt_with_sysmon_filter	`search *`

windows_dll_search_order_hijacking_hunt_with_sysmon_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1574.001	DLL Search Order Hijacking	Defense Evasion

Exploitation

Installation

DE.AE

CIS 10

Default Configuration

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

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	False

This configuration file applies to all detections of type hunting.

Implementation

The search is written against the latest Sysmon TA 4.0 https://splunkbase.splunk.com/app/5709. For this specific event ID 7, the sysmon TA will extract the ImageLoaded name to the loaded_file field which is used in the search to compare against the hijacklibs lookup.

Known False Positives

False positives will be present based on paths. Filter or add other paths to the exclusion as needed. Some applications may legitimately load libraries from non-standard paths.

Associated Analytic Story

References

https://hijacklibs.net/

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

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