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.

Techniques

Sample rules

Windows Known Abused DLL Created

source: splunk
technicques:
- T1574.001
- T1574.002
- T1574

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.

Detection logic


| 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 
| `drop_dm_object_name(Processes)` 
| join max=0 process_guid dest [
| 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 
| `drop_dm_object_name(Filesystem)` 
| lookup hijacklibs_loaded library AS file_name OUTPUT islibrary, ttp, comment as desc 
| lookup hijacklibs_loaded library AS file_name excludes as file_path OUTPUT islibrary as excluded 
| search islibrary = TRUE AND excluded != TRUE 
| stats latest(*) as * by dest process_guid ] 
| where isnotnull(file_name) 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
|  `windows_known_abused_dll_created_filter`