Suspicious FromBase64String Usage On Gzip Archive - Ps Script

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About the rule

Rule Type

Standard

Rule Description

Detects attempts of decoding a base64 Gzip archive in a PowerShell script. This technique is often used as a method to load malicious content into memory afterward.

Severity

Trouble

Rule Requirement

Criteria

Action1: actionname = "PowerShell Script Block Logged" AND SCRIPTEXECUTED contains "FromBase64String" AND SCRIPTEXECUTED contains "MemoryStream" AND SCRIPTEXECUTED contains "H4sI" select Action1.HOSTNAME,Action1.MESSAGE,Action1.SCRIPTEXECUTED

Detection

Execution Mode

realtime

Log Sources

Windows

Author

frack113