YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_WEBSHELL_SECRETSAUCE_Jul23_1

Detects SECRETSAUCE PHP webshells (found after an exploitation of Citrix NetScaler ADC CVE-2023-3519)

WebshellSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compila con YARA-X

Autor: Florian Roth
Fecha: 2023-07-24
Modificada: 2023-12-05
Puntuación / Calidad: 85 / 85

Qué detecta esta regla

Detects SECRETSAUCE PHP webshells (found after an exploitation of Citrix NetScaler ADC CVE-2023-3519)

Define 6 patrones (6 de texto, 0 hex, 0 regex).

Resumen generado a partir de los metadatos y la condición de la regla.

Código de la regla

Descargar .yar

webshell-secretsauce-jul23-1.yarDetection Rule License 1.1

rule SIGNATURE_BASE_WEBSHELL_SECRETSAUCE_Jul23_1 : CVE_2023_3519 FILE
{
	meta:
		description = "Detects SECRETSAUCE PHP webshells (found after an exploitation of Citrix NetScaler ADC CVE-2023-3519)"
		author = "Florian Roth"
		id = "db0542e7-648e-5f60-9838-e07498f58b51"
		date = "2023-07-24"
		modified = "2023-12-05"
		reference = "https://www.mandiant.com/resources/blog/citrix-zero-day-espionage"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/expl_citrix_netscaler_adc_exploitation_cve_2023_3519.yar#L79-L100"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "c762d46ae43a3e10453c2ee17039812a06086ac85bdb000cf8308f5196a9dee2"
		score = 85
		quality = 85
		tags = "CVE-2023-3519, FILE"

	strings:
		$sa1 = "for ($x=0; $x<=1; $x++) {" ascii
		$sa2 = "$_REQUEST[" ascii
		$sa3 = "@eval" ascii
		$sb1 = "public $cmd;" ascii
		$sb2 = "return @eval($a);" ascii
		$sb3 = "$z->run($z->get('openssl_public_decrypt'));"

	condition:
		filesize < 100KB and ( all of ( $sa* ) or 2 of ( $sb* ) )
}

Cadenas (6 patrones)

Identificador	Tipo	Valor	Modificadores
$sa1	texto	"for ($x=0; $x<=1; $x++) {"	ascii
$sa2	texto	"$_REQUEST["	ascii
$sa3	texto	"@eval"	ascii
$sb1	texto	"public $cmd;"	ascii
$sb2	texto	"return @eval($a);"	ascii
$sb3	texto	"$z->run($z->get('openssl_public_decrypt'));"

Condición

filesize < 100KB and ( all of ( $sa* ) or 2 of ( $sb* ) )

En palabras sencillas (Heurística)

El archivo debe ocupar menos de 100KB (un límite barato que descarta archivos grandes).
Deben coincidir todos los patrones de ( $sa* ).
Deben coincidir al menos 2 patrones de ( $sb* ).