YARA Detection Rule: CobaltStrike_Resources_Bind_Bin_v2_5_through_v4_x
Repository: Neo23x0/signature-base
Detects: Cobalt Strike's resources/bind.bin signature for versions 2.5 to 4.x
Author: gssincla@google.com
Reference: https://cloud.google.com/blog/products/identity-security/making-cobalt-strike-harder-for-threat-actors-to-abuse

Pattern signatures:
/*
		31 ??     xor     eax, eax
		AC        lodsb
		C1 ?? 0D  ror     edi, 0Dh
		01 ??     add     edi, eax
		38 ??     cmp     al, ah
		75 ??     jnz     short loc_10000054
		03 [2]    add     edi, [ebp-8]
		3B [2]    cmp     edi, [ebp+24h]
		75 ??     jnz     short loc_1000004A
		5?        pop     eax
		8B ?? 24  mov     ebx, [eax+24h]
		01 ??     add     ebx, edx
		66 8B [2] mov     cx, [ebx+ecx*2]
		8B ?? 1C  mov     ebx, [eax+1Ch]
		01 ??     add     ebx, edx
		8B ?? 8B  mov     eax, [ebx+ecx*4]
		01 ??     add     eax, edx
		89 [3]    mov     [esp+28h+var_4], eax
		5?        pop     ebx
		5?        pop     ebx
	*/

	$apiLocator = {
			31 ?? 
			AC
			C1 ?? 0D 
			01 ?? 
			38 ?? 
			75 ?? 
			03 [2]
			3B [2]
			75 ?? 
			5? 
			8B ?? 24 
			01 ?? 
			66 8B [2]
			8B ?? 1C 
			01 ?? 
			8B ?? 8B 
			01 ?? 
			89 [3]
			5? 
			5? 
		}

    // the signature for the stagers overlap significantly. Looking for bind.bin specific bytes helps delineate sample types
	/*
		5D             p

Detection condition:
$apiLocator and $ws2_32 and $listenaccept

Full rule:
rule CobaltStrike_Resources_Bind_Bin_v2_5_through_v4_x
{
	meta:
		description = "Cobalt Strike's resources/bind.bin signature for versions 2.5 to 4.x"
		hash =  "3727542c0e3c2bf35cacc9e023d1b2d4a1e9e86ee5c62ee5b66184f46ca126d1"
		author = "gssincla@google.com"
		reference = "https://cloud.google.com/blog/products/identity-security/making-cobalt-strike-harder-for-threat-actors-to-abuse"
		date = "2022-11-18"
		
		id = "32f129c1-9845-5843-9e16-7d9af217b8e2"
	strings:
	/*
		31 ??     xor     eax, eax
		AC        lodsb
		C1 ?? 0D  ror     edi, 0Dh
		01 ??     add     edi, eax
		38 ??     cmp     al, ah
		75 ??     jnz     short loc_10000054
		03 [2]    add     edi, [ebp-8]
		3B [2]    cmp     edi, [ebp+24h]
		75 ??     jnz     short loc_1000004A
		5?        pop     eax
		8B ?? 24  mov     ebx, [eax+24h]
		01 ??     add     ebx, edx
		66 8B [2] mov     cx, [ebx+ecx*2]
		8B ?? 1C  mov     ebx, [eax+1Ch]
		01 ??     add     ebx, edx
		8B ?? 8B  mov     eax, [ebx+ecx*4]
		01 ??     add     eax, edx
		89 [3]    mov     [esp+28h+var_4], eax
		5?        pop     ebx
		5?        pop     ebx
	*/

	$apiLocator = {
			31 ?? 
			AC
			C1 ?? 0D 
			01 ?? 
			38 ?? 
			75 ?? 
			03 [2]
			3B [2]
			75 ?? 
			5? 
			8B ?? 24 
			01 ?? 
			66 8B [2]
			8B ?? 1C 
			01 ?? 
			8B ?? 8B 
			01 ?? 
			89 [3]
			5? 
			5? 
		}

    // the signature for the stagers overlap significantly. Looking for bind.bin specific bytes helps delineate sample types
	/*
		5D             pop     ebp
		68 33 32 00 00 push    '23'
		68 77 73 32 5F push    '_2sw'
	*/

	$ws2_32 = {
			5D
			68 33 32 00 00
			68 77 73 32 5F
		}

  // bind.bin, unlike reverse.bin, listens for incoming connections. Using the API hashes for listen and accept is a solid
  // approach to finding bind.bin specific samples
	/*
		5?             push    ebx
		5?             push    edi
		68 B7 E9 38 FF push    listen
		FF ??          call    ebp
		5?             push    ebx
		5?             push    ebx
		5?             push    edi
		68 74