LoFP / there may be legitimate reasons to bypass the powershell execution policy. the powershell script being run with this parameter should be validated to ensure that it is legitimate.

Techniques

• T1059
• T1059.001

Sample rules

Malicious PowerShell Process - Execution Policy Bypass

• source: splunk
• technicques:
  • T1059
  • T1059.001

Description

The following analytic detects PowerShell processes initiated with parameters that bypass the local execution policy for scripts. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions containing specific flags like “-ex” or “bypass.” This activity is significant because bypassing execution policies is a common tactic used by attackers to run malicious scripts undetected. If confirmed malicious, this could allow an attacker to execute arbitrary code, potentially leading to further system compromise, data exfiltration, or persistent access within the environment.

Detection logic

| tstats `security_content_summariesonly` values(Processes.process_id) as process_id, values(Processes.parent_process_id) as parent_process_id values(Processes.process) as process min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` (Processes.process="* -ex*" OR Processes.process="* bypass *") by Processes.process_id, Processes.user, Processes.dest 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `malicious_powershell_process___execution_policy_bypass_filter`