some legitimate applications use long command lines for installs or updates. you should review identified command lines for legitimacy. you may modify the first part of the search to omit legitimate command lines from consideration. if you are seeing more results than desired, you may consider changing the value of threshold in the search to a smaller value. you should also periodically re-run the support search to re-build the ml model on the latest data. you may get unexpected results if the user identified in the results is not present in the data used to build the associated model.

endpoint
splunk

Techniques

Sample rules

Unusually Long Command Line - MLTK

source: splunk
technicques:

Description

Command lines that are extremely long may be indicative of malicious activity on your hosts. This search leverages the Machine Learning Toolkit (MLTK) to help identify command lines with lengths that are unusual for a given user.

Detection logic


| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes by Processes.user Processes.dest Processes.process_name Processes.process 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| eval processlen=len(process) 
| search user!=unknown 
| apply cmdline_pdfmodel threshold=0.01 
| rename "IsOutlier(processlen)" as isOutlier 
| search isOutlier > 0 
| table firstTime lastTime user dest process_name process processlen count 
| `unusually_long_command_line___mltk_filter`