Gootkit is a banking trojan, where large parts are written in javascript (node.JS). It jumps to C/C++-library functions for various tasks.
rule win_gootkit_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2020-12-22" version = "1" description = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.6.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.gootkit" malpedia_rule_date = "20201222" malpedia_hash = "30354d830a29f0fbd3714d93d94dea941d77a130" malpedia_version = "20201023" malpedia_license = "CC BY-SA 4.0" malpedia_sharing = "TLP:WHITE" /* DISCLAIMER * The strings used in this rule have been automatically selected from the * disassembly of memory dumps and unpacked files, using YARA-Signator. * The code and documentation is published here: * https://github.com/fxb-cocacoding/yara-signator * As Malpedia is used as data source, please note that for a given * number of families, only single samples are documented. * This likely impacts the degree of generalization these rules will offer. * Take the described generation method also into consideration when you * apply the rules in your use cases and assign them confidence levels. */ strings: $sequence_0 = { f7f1 81c260ea0000 52 ff15???????? } // n = 4, score = 2000 // f7f1 | div ecx // 81c260ea0000 | add edx, 0xea60 // 52 | push edx // ff15???????? | $sequence_1 = { 83ffff 743f 6a00 6a00 ff75f8 57 ff15???????? } // n = 7, score = 1700 // 83ffff | cmp edi, -1 // 743f | je 0x41 // 6a00 | push 0 // 6a00 | push 0 // ff75f8 | push dword ptr [ebp - 8] // 57 | push edi // ff15???????? | $sequence_2 = { 011c10 8b5dec 115c1004 eb08 } // n = 4, score = 1700 // 011c10 | add dword ptr [eax + edx], ebx // 8b5dec | mov ebx, dword ptr [ebp - 0x14] // 115c1004 | adc dword ptr [eax + edx + 4], ebx // eb08 | jmp 0xa $sequence_3 = { 1adb fec3 6a00 6880000000 6a03 } // n = 5, score = 1700 // 1adb | sbb bl, bl // fec3 | inc bl // 6a00 | push 0 // 6880000000 | push 0x80 // 6a03 | push 3 $sequence_4 = { 894dec 8d0c1a 894dfc 8945f0 85c0 } // n = 5, score = 1700 // 894dec | mov dword ptr [ebp - 0x14], ecx // 8d0c1a | lea ecx, [edx + ebx] // 894dfc | mov dword ptr [ebp - 4], ecx // 8945f0 | mov dword ptr [ebp - 0x10], eax // 85c0 | test eax, eax $sequence_5 = { 1bc0 2145fc ff15???????? 8b45fc 5e } // n = 5, score = 1700 // 1bc0 | sbb eax, eax // 2145fc | and dword ptr [ebp - 4], eax // ff15???????? | // 8b45fc | mov eax, dword ptr [ebp - 4] // 5e | pop esi $sequence_6 = { 41 3bca 72f2 335df0 6a10 58 50 } // n = 7, score = 1700 // 41 | inc ecx // 3bca | cmp ecx, edx // 72f2 | jb 0xfffffff4 // 335df0 | xor ebx, dword ptr [ebp - 0x10] // 6a10 | push 0x10 // 58 | pop eax // 50 | push eax $sequence_7 = { ba64860000 6639540804 7509 8b840888000000 eb04 8b440878 03c1 } // n = 7, score = 1700 // ba64860000 | mov edx, 0x8664 // 6639540804 | cmp word ptr [eax + ecx + 4], dx // 7509 | jne 0xb // 8b840888000000 | mov eax, dword ptr [eax + ecx + 0x88] // eb04 | jmp 6 // 8b440878 | mov eax, dword ptr [eax + ecx + 0x78] // 03c1 | add eax, ecx $sequence_8 = { 52 50 8b4510 99 52 50 8b450c } // n = 7, score = 1400 // 52 | push edx // 50 | push eax // 8b4510 | mov eax, dword ptr [ebp + 0x10] // 99 | cdq // 52 | push edx // 50 | push eax // 8b450c | mov eax, dword ptr [ebp + 0xc] $sequence_9 = { f3aa 68???????? ff15???????? 50 } // n = 4, score = 1200 // f3aa | rep stosb byte ptr es:[edi], al // 68???????? | // ff15???????? | // 50 | push eax $sequence_10 = { 8b7df4 32c0 8b4de4 f3aa } // n = 4, score = 1200 // 8b7df4 | mov edi, dword ptr [ebp - 0xc] // 32c0 | xor al, al // 8b4de4 | mov ecx, dword ptr [ebp - 0x1c] // f3aa | rep stosb byte ptr es:[edi], al $sequence_11 = { 50 68???????? ff15???????? 85c0 7505 e8???????? } // n = 6, score = 1100 // 50 | push eax // 68???????? | // ff15???????? | // 85c0 | test eax, eax // 7505 | jne 7 // e8???????? | $sequence_12 = { 50 e8???????? 83c40c 68fd000000 } // n = 4, score = 1100 // 50 | push eax // e8???????? | // 83c40c | add esp, 0xc // 68fd000000 | push 0xfd $sequence_13 = { 50 8b4508 8b00 99 52 } // n = 5, score = 1000 // 50 | push eax // 8b4508 | mov eax, dword ptr [ebp + 8] // 8b00 | mov eax, dword ptr [eax] // 99 | cdq // 52 | push edx $sequence_14 = { c705????????02000000 8be5 5d c3 } // n = 4, score = 900 // c705????????02000000 | // 8be5 | mov esp, ebp // 5d | pop ebp // c3 | ret $sequence_15 = { 7514 c705????????01000000 c705????????02000000 8be5 } // n = 4, score = 900 // 7514 | jne 0x16 // c705????????01000000 | // c705????????02000000 | // 8be5 | mov esp, ebp $sequence_16 = { e8???????? 6a0c 6a08 ff15???????? } // n = 4, score = 800 // e8???????? | // 6a0c | push 0xc // 6a08 | push 8 // ff15???????? | $sequence_17 = { 68???????? 51 51 ff15???????? 50 } // n = 5, score = 300 // 68???????? | // 51 | push ecx // 51 | push ecx // ff15???????? | // 50 | push eax $sequence_18 = { 53 53 53 8901 } // n = 4, score = 300 // 53 | push ebx // 53 | push ebx // 53 | push ebx // 8901 | mov dword ptr [ecx], eax $sequence_19 = { 8b0d???????? 5f a3???????? a1???????? 5e 85c0 } // n = 6, score = 200 // 8b0d???????? | // 5f | pop edi // a3???????? | // a1???????? | // 5e | pop esi // 85c0 | test eax, eax $sequence_20 = { 034e10 8d852cfdffff 898de4fdffff 50 } // n = 4, score = 200 // 034e10 | add ecx, dword ptr [esi + 0x10] // 8d852cfdffff | lea eax, [ebp - 0x2d4] // 898de4fdffff | mov dword ptr [ebp - 0x21c], ecx // 50 | push eax $sequence_21 = { 0f114f20 0f104840 0f114730 0f104050 } // n = 4, score = 200 // 0f114f20 | movups xmmword ptr [edi + 0x20], xmm1 // 0f104840 | movups xmm1, xmmword ptr [eax + 0x40] // 0f114730 | movups xmmword ptr [edi + 0x30], xmm0 // 0f104050 | movups xmm0, xmmword ptr [eax + 0x50] $sequence_22 = { 0f114730 0f104050 0f114f40 0f104860 0f114750 0f114f60 b801000000 } // n = 7, score = 200 // 0f114730 | movups xmmword ptr [edi + 0x30], xmm0 // 0f104050 | movups xmm0, xmmword ptr [eax + 0x50] // 0f114f40 | movups xmmword ptr [edi + 0x40], xmm1 // 0f104860 | movups xmm1, xmmword ptr [eax + 0x60] // 0f114750 | movups xmmword ptr [edi + 0x50], xmm0 // 0f114f60 | movups xmmword ptr [edi + 0x60], xmm1 // b801000000 | mov eax, 1 $sequence_23 = { 813a50450000 7541 8b82d8000000 03c1 3bd8 7235 8b82dc000000 } // n = 7, score = 200 // 813a50450000 | cmp dword ptr [edx], 0x4550 // 7541 | jne 0x43 // 8b82d8000000 | mov eax, dword ptr [edx + 0xd8] // 03c1 | add eax, ecx // 3bd8 | cmp ebx, eax // 7235 | jb 0x37 // 8b82dc000000 | mov eax, dword ptr [edx + 0xdc] $sequence_24 = { 83faff 7508 ff15???????? 8bd0 } // n = 4, score = 200 // 83faff | cmp edx, -1 // 7508 | jne 0xa // ff15???????? | // 8bd0 | mov edx, eax $sequence_25 = { ff15???????? ffc3 83fb0a 7cd5 33c0 } // n = 5, score = 200 // ff15???????? | // ffc3 | inc ebx // 83fb0a | cmp ebx, 0xa // 7cd5 | jl 0xffffffd7 // 33c0 | xor eax, eax $sequence_26 = { 391d???????? 7428 85c0 7424 83ec0c ba???????? b9???????? } // n = 7, score = 200 // 391d???????? | // 7428 | je 0x2a // 85c0 | test eax, eax // 7424 | je 0x26 // 83ec0c | sub esp, 0xc // ba???????? | // b9???????? | $sequence_27 = { 0f104820 0f114710 0f104030 0f114f20 } // n = 4, score = 200 // 0f104820 | movups xmm1, xmmword ptr [eax + 0x20] // 0f114710 | movups xmmword ptr [edi + 0x10], xmm0 // 0f104030 | movups xmm0, xmmword ptr [eax + 0x30] // 0f114f20 | movups xmmword ptr [edi + 0x20], xmm1 $sequence_28 = { 53 33db e8???????? ff15???????? 8bc8 } // n = 5, score = 200 // 53 | push ebx // 33db | xor ebx, ebx // e8???????? | // ff15???????? | // 8bc8 | mov ecx, eax $sequence_29 = { 0f104850 0f114f50 0f104060 0f114760 8b4070 894770 be01000000 } // n = 7, score = 200 // 0f104850 | movups xmm1, xmmword ptr [eax + 0x50] // 0f114f50 | movups xmmword ptr [edi + 0x50], xmm1 // 0f104060 | movups xmm0, xmmword ptr [eax + 0x60] // 0f114760 | movups xmmword ptr [edi + 0x60], xmm0 // 8b4070 | mov eax, dword ptr [eax + 0x70] // 894770 | mov dword ptr [edi + 0x70], eax // be01000000 | mov esi, 1 $sequence_30 = { 8b7df4 85ff 7414 57 8bce } // n = 5, score = 200 // 8b7df4 | mov edi, dword ptr [ebp - 0xc] // 85ff | test edi, edi // 7414 | je 0x16 // 57 | push edi // 8bce | mov ecx, esi $sequence_31 = { ff15???????? 8bd0 83fa01 7e18 } // n = 4, score = 200 // ff15???????? | // 8bd0 | mov edx, eax // 83fa01 | cmp edx, 1 // 7e18 | jle 0x1a $sequence_32 = { ff15???????? 85c0 7550 ff15???????? 8bf8 893d???????? } // n = 6, score = 200 // ff15???????? | // 85c0 | test eax, eax // 7550 | jne 0x52 // ff15???????? | // 8bf8 | mov edi, eax // 893d???????? | condition: 7 of them and filesize < 516096 }
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