/*
	Yara Rule Set
	Author: YarGen Rule Generator
	Date: 2016-05-21
	Identifier: No PowerShell
*/

rule No_PowerShell {
	meta:
		description = "Detects an C# executable used to circumvent PowerShell detection - file nps.exe"
		license = "Detection Rule License 1.1 https://github.com/Neo23x0/signature-base/blob/master/LICENSE"
		author = "Florian Roth (Nextron Systems)"
		reference = "https://github.com/Ben0xA/nps"
		date = "2016-05-21"
		score = 80
		hash1 = "64f811b99eb4ae038c88c67ee0dc9b150445e68a2eb35ff1a0296533ae2edd71"
		id = "362a61bc-2c10-5076-93be-9f8b5a9ae8ba"
	strings:
		$s1 = "nps.exe -encodedcommand {base64_encoded_command}" fullword wide
		$s2 = "c:\\Development\\ghps\\nps\\nps\\obj\\x86\\Release\\nps.pdb" fullword ascii
	condition:
		( uint16(0) == 0x5a4d and filesize < 40KB and ( 1 of ($s*) ) ) or ( all of them )
}