Techniques
Sample rules
Malicious PowerShell Process - Encoded Command
- source: splunk
- technicques:
- T1027
Description
The following analytic identifies the use of the EncodedCommand PowerShell parameter. This is typically used by Administrators to run complex scripts, but commonly used by adversaries to hide their code. The analytic identifies all variations of EncodedCommand, as PowerShell allows the ability to shorten the parameter. For example enc, enco, encod and so forth. In addition, through our research it was identified that PowerShell will interpret different command switch types beyond the hyphen. We have added endash, emdash, horizontal bar, and forward slash. During triage, review parallel events to determine legitimacy. Tune as needed based on admin scripts in use. Alternatively, may use regex per matching here https://regexr.com/662ov.
Detection logic
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` by Processes.user Processes.process_name Processes.process Processes.parent_process_name Processes.original_file_name Processes.dest Processes.process_id
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| where match(process,"(?i)[\-
|\/
|–
|—
|―]e(nc*o*d*e*d*c*o*m*m*a*n*d*)*\s+[^-]")
| `malicious_powershell_process___encoded_command_filter`