Potential AMSI Bypass Via .NET Reflection
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About the rule
Rule Type
Standard
Rule Description
Detects Request to "amsiInitFailed" that can be used to disable AMSI Scanning
Severity
Trouble
Rule Requirement
Criteria
Action1:
actionname = "Process started" AND (COMMANDLINE contains "System.Management.Automation.AmsiUtils" AND COMMANDLINE contains "amsiInitFailed") OR (COMMANDLINE contains "[Ref].Assembly.GetType" AND COMMANDLINE contains "SetValue($null,$true)" AND COMMANDLINE contains "NonPublic,Static")
select Action1.HOSTNAME,Action1.MESSAGE,Action1.COMMANDLINE,Action1.FILE_NAME,Action1.PROCESSNAME,Action1.USERNAME,Action1.PARENTPROCESSNAME,Action1.DOMAIN,Action1.ORIGINALFILENAME,Action1.PARENTPROCESSID,Action1.PROCESSID,Action1.PRODUCT_NAME,Action1.SECURITYID
Detection
Execution Mode
realtime
Log Sources
Windows
Author
Markus Neis, @Kostastsale
