LoFP / false positives may only pertain to it not being related to empire, but another framework. filter as needed if any applications use the same pattern.

Techniques

• T1059
• T1059.001

Sample rules

Detect Empire with PowerShell Script Block Logging

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

Description

The following analytic utilizes PowerShell Script Block Logging (EventCode=4104) to identify suspicious PowerShell execution. Script Block Logging captures the command sent to PowerShell, the full command to be executed. Upon enabling, logs will output to Windows event logs. Dependent upon volume, enable on critical endpoints or all.

This analytic identifies the common PowerShell stager used by PowerShell-Empire. Each stager that may use PowerShell all uses the same pattern. The initial HTTP will be base64 encoded and use system.net.webclient. Note that some obfuscation may evade the analytic. During triage, review parallel processes using an EDR product or 4688 events. It will be important to understand the timeline of events around this activity. Review the entire logged PowerShell script block.

Detection logic

`powershell` EventCode=4104  (ScriptBlockText=*system.net.webclient* AND ScriptBlockText=*frombase64string*) 
| stats count min(_time) as firstTime max(_time) as lastTime by Opcode Computer UserID EventCode ScriptBlockText 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `detect_empire_with_powershell_script_block_logging_filter`