rule elknot_xor : ELF PE DDoS XOR BillGates  
{
meta:  
    author = "liuya@360.cn"
    description = "elknot/Billgates variants with XOR like C2 encryption scheme"
	reference = "http://blog.netlab.360.com/new-elknot-billgates-variant-with-xor-like-c2-configuration-encryption-scheme/"
    date = "2015-09-12"

strings:  
   //md5=474429d9da170e733213940acc9a2b1c
   /*
   seg000:08130801 68 00 09 13 08                push    offset dword_8130900
   seg000:08130806 83 3D 30 17 13 08 02          cmp     ds:dword_8131730, 2
   seg000:0813080D 75 07                         jnz     short loc_8130816
   seg000:0813080F 81 04 24 00 01 00 00          add     dword ptr [esp], 100h
   seg000:08130816               loc_8130816:                           
   seg000:08130816 50                            push    eax
   seg000:08130817 E8 15 00 00 00                call    sub_8130831
   seg000:0813081C E9 C8 F6 F5 FF                jmp     near ptr 808FEE9h
   */
   $decrypt_c2_func_1 = {08 83 [5] 02 75 07 81 04 24 00 01 00 00 50 e8 [4] e9}

   // md5=2579aa65a28c32778790ec1c673abc49
   /*
   .rodata:08104D20 E8 00 00 00 00                call    $+5
   .rodata:08104D25 87 1C 24                      xchg    ebx, [esp+4+var_4] ;
   .rodata:08104D28 83 EB 05                      sub     ebx, 5
   .rodata:08104D2B 8D 83 00 FD FF FF             lea     eax, [ebx-300h]
   .rodata:08104D31 83 BB 10 CA 02 00 02          cmp   dword ptr [ebx+2CA10h], 2
   .rodata:08104D38 75 05                         jnz     short loc_8104D3F
   .rodata:08104D3A 05 00 01 00 00                add     eax, 100h
   .rodata:08104D3F               loc_8104D3F:                           
   .rodata:08104D3F 50                            push    eax
   .rodata:08104D40 FF 74 24 10                   push    [esp+8+strsVector]
   */
   $decrypt_c2_func_2 = {e8 00 00 00 00 87 [2] 83 eb 05 8d 83 [4] 83 bb [4] 02 75 05}

condition:  
    1 of ($decrypt_c2_func_*)
}