Suspicious PowerShell Invocations with Obfuscation or Download
This rule detects suspicious PowerShell invocations characterized by specific command parameters often used in malicious activities. It looks for combinations of parameters like '-nop', '-w hidden', '-c', and '[Convert]::FromBase64String' for base64 encoded commands; '-w hidden', '-noni', '-nop', '-c', 'iex', and 'New-Object' for obfuscated execution; '-w hidden', '-ep bypass', and '-Enc' for encoded command execution; PowerShell commands interacting with 'reg add' to modify 'Run' keys for persistence; and PowerShell using 'New-Object System.Net.WebClient' with '.Download' for downloading content from the internet, often with 'bypass' and 'hidden' window styles. These patterns are commonly associated with malware, post-exploitation frameworks, and adversary tradecraft.
Sigma
