Powershell Base64 Encoded MpPreference Cmdlet
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About the rule
Rule Type
Standard
Rule Description
Detects base64 encoded "MpPreference" PowerShell cmdlet code that tries to modifies or tamper with Windows Defender AV
Severity
Trouble
Rule Requirement
Criteria
Action1: actionname = "Process started" AND (COMMANDLINE contains "QWRkLU1wUHJlZmVyZW5jZS,FkZC1NcFByZWZlcmVuY2Ug,BZGQtTXBQcmVmZXJlbmNlI" OR COMMANDLINE contains "U2V0LU1wUHJlZmVyZW5jZS,NldC1NcFByZWZlcmVuY2Ug,TZXQtTXBQcmVmZXJlbmNlI" OR COMMANDLINE contains "YWRkLW1wcHJlZmVyZW5jZS,FkZC1tcHByZWZlcmVuY2Ug,hZGQtbXBwcmVmZXJlbmNlI" OR COMMANDLINE contains "c2V0LW1wcHJlZmVyZW5jZS,NldC1tcHByZWZlcmVuY2Ug,zZXQtbXBwcmVmZXJlbmNlI") OR COMMANDLINE contains "QQBkAGQALQBNAHAAUAByAGUAZgBlAHIAZQBuAGMAZQAgA,EAZABkAC0ATQBwAFAAcgBlAGYAZQByAGUAbgBjAGUAIA,BAGQAZAAtAE0AcABQAHIAZQBmAGUAcgBlAG4AYwBlACAA,UwBlAHQALQBNAHAAUAByAGUAZgBlAHIAZQBuAGMAZQAgA,MAZQB0AC0ATQBwAFAAcgBlAGYAZQByAGUAbgBjAGUAIA,TAGUAdAAtAE0AcABQAHIAZQBmAGUAcgBlAG4AYwBlACAA,YQBkAGQALQBtAHAAcAByAGUAZgBlAHIAZQBuAGMAZQAgA,EAZABkAC0AbQBwAHAAcgBlAGYAZQByAGUAbgBjAGUAIA,hAGQAZAAtAG0AcABwAHIAZQBmAGUAcgBlAG4AYwBlACAA,cwBlAHQALQBtAHAAcAByAGUAZgBlAHIAZQBuAGMAZQAgA,MAZQB0AC0AbQBwAHAAcgBlAGYAZQByAGUAbgBjAGUAIA,zAGUAdAAtAG0AcABwAHIAZQBmAGUAcgBlAG4AYwBlACAA" select Action1.HOSTNAME,Action1.MESSAGE,Action1.COMMANDLINE,Action1.FILE_NAME,Action1.PROCESSNAME,Action1.USERNAME,Action1.PARENTPROCESSNAME
Detection
Execution Mode
realtime
Log Sources
Windows
Author
Florian Roth (Nextron Systems)
