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 = "2020-08-17" version = "1" description = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.4.0" tool_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.gootkit" malpedia_rule_date = "20200817" malpedia_hash = "8c895fd01eccb47a6225bcb1a3ba53cbb98644c5" malpedia_version = "20200817" 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 / approach 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 = 1900 // f7f1 | div ecx // 81c260ea0000 | add edx, 0xea60 // 52 | push edx // ff15???????? | $sequence_1 = { 33d2 50 6a00 8bce e8???????? 8b7dfc } // n = 6, score = 1600 // 33d2 | xor edx, edx // 50 | push eax // 6a00 | push 0 // 8bce | mov ecx, esi // e8???????? | // 8b7dfc | mov edi, dword ptr [ebp - 4] $sequence_2 = { 85db 7431 3bfb 752d 56 } // n = 5, score = 1600 // 85db | test ebx, ebx // 7431 | je 0x33 // 3bfb | cmp edi, ebx // 752d | jne 0x2f // 56 | push esi $sequence_3 = { 50 53 56 57 51 51 } // n = 6, score = 1600 // 50 | push eax // 53 | push ebx // 56 | push esi // 57 | push edi // 51 | push ecx // 51 | push ecx $sequence_4 = { 03c1 03f9 8945f8 83d300 897de4 } // n = 5, score = 1600 // 03c1 | add eax, ecx // 03f9 | add edi, ecx // 8945f8 | mov dword ptr [ebp - 8], eax // 83d300 | adc ebx, 0 // 897de4 | mov dword ptr [ebp - 0x1c], edi $sequence_5 = { 8b4dfc 83c602 8b45f8 83c104 40 894dfc 8945f8 } // n = 7, score = 1600 // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 83c602 | add esi, 2 // 8b45f8 | mov eax, dword ptr [ebp - 8] // 83c104 | add ecx, 4 // 40 | inc eax // 894dfc | mov dword ptr [ebp - 4], ecx // 8945f8 | mov dword ptr [ebp - 8], eax $sequence_6 = { 50 8d45f0 0f45f1 50 } // n = 4, score = 1600 // 50 | push eax // 8d45f0 | lea eax, [ebp - 0x10] // 0f45f1 | cmovne esi, ecx // 50 | push eax $sequence_7 = { 8955f4 8b0d???????? 6a02 5b } // n = 4, score = 1600 // 8955f4 | mov dword ptr [ebp - 0xc], edx // 8b0d???????? | // 6a02 | push 2 // 5b | pop ebx $sequence_8 = { 52 50 8b4510 99 52 50 8b450c } // n = 7, score = 1300 // 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 e8???????? 83c40c 68fd000000 } // n = 4, score = 1100 // 50 | push eax // e8???????? | // 83c40c | add esp, 0xc // 68fd000000 | push 0xfd $sequence_12 = { 68???????? ff15???????? 85c0 7405 e8???????? } // n = 5, score = 1000 // 68???????? | // ff15???????? | // 85c0 | test eax, eax // 7405 | je 7 // e8???????? | $sequence_13 = { 7514 c705????????01000000 c705????????02000000 8be5 } // n = 4, score = 900 // 7514 | jne 0x16 // c705????????01000000 | // c705????????02000000 | // 8be5 | mov esp, ebp $sequence_14 = { 50 8b4508 8b00 99 52 50 } // n = 6, score = 900 // 50 | push eax // 8b4508 | mov eax, dword ptr [ebp + 8] // 8b00 | mov eax, dword ptr [eax] // 99 | cdq // 52 | push edx // 50 | push eax $sequence_15 = { c705????????02000000 8be5 5d c3 } // n = 4, score = 900 // c705????????02000000 | // 8be5 | mov esp, ebp // 5d | pop ebp // c3 | ret $sequence_16 = { e8???????? 6a0c 6a08 ff15???????? } // n = 4, score = 700 // 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 = { ff15???????? 8bd0 83fa01 7e18 } // n = 4, score = 200 // ff15???????? | // 8bd0 | mov edx, eax // 83fa01 | cmp edx, 1 // 7e18 | jle 0x1a $sequence_20 = { ba???????? b9???????? e8???????? 3935???????? 7412 } // n = 5, score = 200 // ba???????? | // b9???????? | // e8???????? | // 3935???????? | // 7412 | je 0x14 $sequence_21 = { 85c0 56 0f45ca 894dfc ff15???????? } // n = 5, score = 200 // 85c0 | test eax, eax // 56 | push esi // 0f45ca | cmovne ecx, edx // 894dfc | mov dword ptr [ebp - 4], ecx // ff15???????? | $sequence_22 = { 0f114f40 0f104860 0f114750 0f114f60 } // n = 4, score = 200 // 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 $sequence_23 = { 7541 8b82d8000000 03c1 3bd8 7235 8b82dc000000 0382d8000000 } // n = 7, score = 200 // 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] // 0382d8000000 | add eax, dword ptr [edx + 0xd8] $sequence_24 = { 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_25 = { 0f104010 0f110f 0f104820 0f114710 } // n = 4, score = 200 // 0f104010 | movups xmm0, xmmword ptr [eax + 0x10] // 0f110f | movups xmmword ptr [edi], xmm1 // 0f104820 | movups xmm1, xmmword ptr [eax + 0x20] // 0f114710 | movups xmmword ptr [edi + 0x10], xmm0 $sequence_26 = { 83faff 7508 ff15???????? 8bd0 } // n = 4, score = 200 // 83faff | cmp edx, -1 // 7508 | jne 0xa // ff15???????? | // 8bd0 | mov edx, eax $sequence_27 = { 8d442408 50 6802020000 ff15???????? 6a06 } // n = 5, score = 200 // 8d442408 | lea eax, [esp + 8] // 50 | push eax // 6802020000 | push 0x202 // ff15???????? | // 6a06 | push 6 $sequence_28 = { 3bd8 7323 8b33 eb19 3ce9 7508 } // n = 6, score = 200 // 3bd8 | cmp ebx, eax // 7323 | jae 0x25 // 8b33 | mov esi, dword ptr [ebx] // eb19 | jmp 0x1b // 3ce9 | cmp al, 0xe9 // 7508 | jne 0xa $sequence_29 = { 8b8de4fdffff 8b36 85f6 75a2 } // n = 4, score = 200 // 8b8de4fdffff | mov ecx, dword ptr [ebp - 0x21c] // 8b36 | mov esi, dword ptr [esi] // 85f6 | test esi, esi // 75a2 | jne 0xffffffa4 $sequence_30 = { 0f104850 0f114f50 0f104060 0f114760 8b4070 894770 } // n = 6, 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 $sequence_31 = { 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_32 = { 85c0 7510 8d4864 ff15???????? ffc3 83fb0a 7cd5 } // n = 7, score = 200 // 85c0 | test eax, eax // 7510 | jne 0x12 // 8d4864 | lea ecx, [eax + 0x64] // ff15???????? | // ffc3 | inc ebx // 83fb0a | cmp ebx, 0xa // 7cd5 | jl 0xffffffd7 condition: 7 of them and filesize < 516096 }
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