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 = "2021-06-10" version = "1" description = "Detects win.gootkit." info = "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 = "20210604" malpedia_hash = "be09d5d71e77373c0f538068be31a2ad4c69cfbd" malpedia_version = "20210616" 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 = { 8d7308 56 ffd7 8bd0 33db 33c9 } // n = 6, score = 1700 // 8d7308 | lea esi, dword ptr [ebx + 8] // 56 | push esi // ffd7 | call edi // 8bd0 | mov edx, eax // 33db | xor ebx, ebx // 33c9 | xor ecx, ecx $sequence_1 = { 3b45f0 72d6 eb09 0fb706 8b4dec 8d3c81 8bc7 } // n = 7, score = 1700 // 3b45f0 | cmp eax, dword ptr [ebp - 0x10] // 72d6 | jb 0xffffffd8 // eb09 | jmp 0xb // 0fb706 | movzx eax, word ptr [esi] // 8b4dec | mov ecx, dword ptr [ebp - 0x14] // 8d3c81 | lea edi, dword ptr [ecx + eax*4] // 8bc7 | mov eax, edi $sequence_2 = { 752d 56 8b35???????? 81c704010000 6a00 ffd6 50 } // n = 7, score = 1700 // 752d | jne 0x2f // 56 | push esi // 8b35???????? | // 81c704010000 | add edi, 0x104 // 6a00 | push 0 // ffd6 | call esi // 50 | push eax $sequence_3 = { 8b463c b94c010000 66394c3004 7510 33c9 41 e8???????? } // n = 7, score = 1700 // 8b463c | mov eax, dword ptr [esi + 0x3c] // b94c010000 | mov ecx, 0x14c // 66394c3004 | cmp word ptr [eax + esi + 4], cx // 7510 | jne 0x12 // 33c9 | xor ecx, ecx // 41 | inc ecx // e8???????? | $sequence_4 = { 8bfb 895dec f3aa 8b3d???????? 8d45f8 50 } // n = 6, score = 1700 // 8bfb | mov edi, ebx // 895dec | mov dword ptr [ebp - 0x14], ebx // f3aa | rep stosb byte ptr es:[edi], al // 8b3d???????? | // 8d45f8 | lea eax, dword ptr [ebp - 8] // 50 | push eax $sequence_5 = { 33d2 50 6a00 8bce e8???????? } // n = 5, score = 1700 // 33d2 | xor edx, edx // 50 | push eax // 6a00 | push 0 // 8bce | mov ecx, esi // e8???????? | $sequence_6 = { 8d3c81 8bc7 5e eb02 } // n = 4, score = 1700 // 8d3c81 | lea edi, dword ptr [ecx + eax*4] // 8bc7 | mov eax, edi // 5e | pop esi // eb02 | jmp 4 $sequence_7 = { 8d45f0 50 6a04 8d45ec 50 57 ff15???????? } // n = 7, score = 1700 // 8d45f0 | lea eax, dword ptr [ebp - 0x10] // 50 | push eax // 6a04 | push 4 // 8d45ec | lea eax, dword ptr [ebp - 0x14] // 50 | push eax // 57 | push edi // ff15???????? | $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 = { 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_10 = { f3aa 68???????? ff15???????? 50 } // n = 4, score = 1200 // f3aa | rep stosb byte ptr es:[edi], al // 68???????? | // ff15???????? | // 50 | push eax $sequence_11 = { 50 e8???????? 83c40c 68fd000000 } // n = 4, score = 1100 // 50 | push eax // e8???????? | // 83c40c | add esp, 0xc // 68fd000000 | push 0xfd $sequence_12 = { 50 68???????? ff15???????? 85c0 7505 e8???????? } // n = 6, score = 1100 // 50 | push eax // 68???????? | // ff15???????? | // 85c0 | test eax, eax // 7505 | jne 7 // e8???????? | $sequence_13 = { 50 8b4508 8b00 99 } // n = 4, score = 1000 // 50 | push eax // 8b4508 | mov eax, dword ptr [ebp + 8] // 8b00 | mov eax, dword ptr [eax] // 99 | cdq $sequence_14 = { 7514 c705????????01000000 c705????????02000000 8be5 } // n = 4, score = 900 // 7514 | jne 0x16 // c705????????01000000 | // c705????????02000000 | // 8be5 | mov esp, ebp $sequence_15 = { c705????????02000000 8be5 5d c3 55 } // n = 5, score = 900 // c705????????02000000 | // 8be5 | mov esp, ebp // 5d | pop ebp // c3 | ret // 55 | push ebp $sequence_16 = { 6808020000 6a00 ff15???????? 50 ff15???????? } // n = 5, score = 800 // 6808020000 | push 0x208 // 6a00 | push 0 // ff15???????? | // 50 | push eax // ff15???????? | $sequence_17 = { e8???????? 6a0c 6a08 ff15???????? 50 } // n = 5, score = 800 // e8???????? | // 6a0c | push 0xc // 6a08 | push 8 // ff15???????? | // 50 | push eax $sequence_18 = { e8???????? 8d45fc 50 6a01 6a01 6a00 } // n = 6, score = 600 // e8???????? | // 8d45fc | lea eax, dword ptr [ebp - 4] // 50 | push eax // 6a01 | push 1 // 6a01 | push 1 // 6a00 | push 0 $sequence_19 = { 68???????? 51 51 ff15???????? 50 } // n = 5, score = 300 // 68???????? | // 51 | push ecx // 51 | push ecx // ff15???????? | // 50 | push eax $sequence_20 = { 53 53 53 8901 } // n = 4, score = 300 // 53 | push ebx // 53 | push ebx // 53 | push ebx // 8901 | mov dword ptr [ecx], eax $sequence_21 = { 7510 8d4864 ff15???????? ffc3 } // n = 4, score = 200 // 7510 | jne 0x12 // 8d4864 | lea ecx, dword ptr [eax + 0x64] // ff15???????? | // ffc3 | inc ebx $sequence_22 = { 8bc8 e8???????? 3935???????? 7412 } // n = 4, score = 200 // 8bc8 | mov ecx, eax // e8???????? | // 3935???????? | // 7412 | je 0x14 $sequence_23 = { 0f114740 0f104850 0f114f50 0f104060 0f114760 8b4070 } // n = 6, score = 200 // 0f114740 | movups xmmword ptr [edi + 0x40], xmm0 // 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] $sequence_24 = { 50 68060000c8 56 ff15???????? 8b4dfc 33d2 85c0 } // n = 7, score = 200 // 50 | push eax // 68060000c8 | push 0xc8000006 // 56 | push esi // ff15???????? | // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 33d2 | xor edx, edx // 85c0 | test eax, eax $sequence_25 = { ff15???????? 85c0 7510 8d4864 } // n = 4, score = 200 // ff15???????? | // 85c0 | test eax, eax // 7510 | jne 0x12 // 8d4864 | lea ecx, dword ptr [eax + 0x64] $sequence_26 = { 0f104030 0f114f20 0f104840 0f114730 } // n = 4, score = 200 // 0f104030 | movups xmm0, xmmword ptr [eax + 0x30] // 0f114f20 | movups xmmword ptr [edi + 0x20], xmm1 // 0f104840 | movups xmm1, xmmword ptr [eax + 0x40] // 0f114730 | movups xmmword ptr [edi + 0x30], xmm0 $sequence_27 = { 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_28 = { a3???????? 391d???????? 7428 85c0 } // n = 4, score = 200 // a3???????? | // 391d???????? | // 7428 | je 0x2a // 85c0 | test eax, eax $sequence_29 = { 7552 807e0125 754c 8b5e02 8d45e4 6a1c } // n = 6, score = 200 // 7552 | jne 0x54 // 807e0125 | cmp byte ptr [esi + 1], 0x25 // 754c | jne 0x4e // 8b5e02 | mov ebx, dword ptr [esi + 2] // 8d45e4 | lea eax, dword ptr [ebp - 0x1c] // 6a1c | push 0x1c $sequence_30 = { 55 8bec 81ecd4020000 ff15???????? } // n = 4, score = 200 // 55 | push ebp // 8bec | mov ebp, esp // 81ecd4020000 | sub esp, 0x2d4 // ff15???????? | $sequence_31 = { ff15???????? 8bd0 83fa01 7e18 } // n = 4, score = 200 // ff15???????? | // 8bd0 | mov edx, eax // 83fa01 | cmp edx, 1 // 7e18 | jle 0x1a $sequence_32 = { 0f114730 0f104050 0f114f40 0f104860 } // n = 4, 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] $sequence_33 = { 0f104060 0f114760 8b4070 894770 be01000000 ff15???????? } // n = 6, score = 200 // 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 // ff15???????? | condition: 7 of them and filesize < 516096 }
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