Detection: Windows Known Abused DLL Created

Description

The following analytic identifies the creation of Dynamic Link Libraries (DLLs) with a known history of exploitation in atypical locations. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and filesystem events. This activity is significant as it may indicate DLL search order hijacking or sideloading, techniques used by attackers to execute arbitrary code, maintain persistence, or escalate privileges. If confirmed malicious, this activity could allow attackers to blend in with legitimate operations, posing a severe threat to system integrity and security.

Search

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes where Processes.parent_process_name!="unknown" Processes.process_name=* Processes.process_guid!=null by _time span=1h Processes.dest Processes.user Processes.process_guid Processes.process_name Processes.process Processes.parent_process Processes.parent_process_name 
 3| `drop_dm_object_name(Processes)` 
 4| join max=0 process_guid dest [
 5| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\users\\*","*\\Windows\Temp\\*","*\\programdata\\*") Filesystem.file_name="*.dll" by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path Filesystem.process_guid 
 6| `drop_dm_object_name(Filesystem)` 
 7| lookup hijacklibs_loaded library AS file_name OUTPUT islibrary, ttp, comment as desc 
 8| lookup hijacklibs_loaded library AS file_name excludes as file_path OUTPUT islibrary as excluded 
 9| search islibrary = TRUE AND excluded != TRUE 
10| stats latest(*) as * by dest process_guid ] 
11| where isnotnull(file_name) 
12| `security_content_ctime(firstTime)` 
13| `security_content_ctime(lastTime)` 
14|  `windows_known_abused_dll_created_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon EventID 11	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-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 and Filesystem nodes 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

This analytic may flag instances where DLLs are loaded by user mode programs for entirely legitimate and benign purposes. It is important for users to be aware that false positives are not only possible but likely, and that careful tuning of this analytic is necessary to distinguish between malicious activity and normal, everyday operations of applications. This may involve adjusting thresholds, whitelisting known good software, or incorporating additional context from other security tools and logs to reduce the rate of false positives.

Associated Analytic Story

• Living Off The Land

• Windows Defense Evasion Tactics

Risk Based Analytics (RBA)

References

• https://attack.mitre.org/techniques/T1574/002/

• https://hijacklibs.net/api/

• https://wietze.github.io/blog/hijacking-dlls-in-windows

• https://github.com/olafhartong/sysmon-modular/pull/195/files

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: 3