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 = "2021-10-07" 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 = "20211007" malpedia_hash = "e5b790e0f888f252d49063a1251ca60ec2832535" malpedia_version = "20211008" 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 = { 895df0 85db 7474 8b7ddc } // n = 4, score = 1700 // 895df0 | mov dword ptr [ebp - 0x10], ebx // 85db | test ebx, ebx // 7474 | je 0x76 // 8b7ddc | mov edi, dword ptr [ebp - 0x24] $sequence_1 = { 50 6a00 8bce e8???????? 8b7dfc 59 } // n = 6, score = 1700 // 50 | push eax // 6a00 | push 0 // 8bce | mov ecx, esi // e8???????? | // 8b7dfc | mov edi, dword ptr [ebp - 4] // 59 | pop ecx $sequence_2 = { 85d2 740e 0fbe0431 c1cf0d } // n = 4, score = 1700 // 85d2 | test edx, edx // 740e | je 0x10 // 0fbe0431 | movsx eax, byte ptr [ecx + esi] // c1cf0d | ror edi, 0xd $sequence_3 = { 0fb75b06 03f8 33f6 3b570c } // n = 4, score = 1700 // 0fb75b06 | movzx ebx, word ptr [ebx + 6] // 03f8 | add edi, eax // 33f6 | xor esi, esi // 3b570c | cmp edx, dword ptr [edi + 0xc] $sequence_4 = { 8bcf e8???????? 6806000200 8bd7 e8???????? } // n = 5, score = 1700 // 8bcf | mov ecx, edi // e8???????? | // 6806000200 | push 0x20006 // 8bd7 | mov edx, edi // e8???????? | $sequence_5 = { ff75fc ffd7 33c9 c745f804000000 } // n = 4, score = 1700 // ff75fc | push dword ptr [ebp - 4] // ffd7 | call edi // 33c9 | xor ecx, ecx // c745f804000000 | mov dword ptr [ebp - 8], 4 $sequence_6 = { 8b5dec 115c1004 eb08 25ff0f0000 } // n = 4, score = 1700 // 8b5dec | mov ebx, dword ptr [ebp - 0x14] // 115c1004 | adc dword ptr [eax + edx + 4], ebx // eb08 | jmp 0xa // 25ff0f0000 | and eax, 0xfff $sequence_7 = { 57 6a10 59 bf???????? c745b47272656e f3aa } // n = 6, score = 1700 // 57 | push edi // 6a10 | push 0x10 // 59 | pop ecx // bf???????? | // c745b47272656e | mov dword ptr [ebp - 0x4c], 0x6e657272 // f3aa | rep stosb byte ptr es:[edi], al $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 = { 8b4508 8b00 99 52 } // n = 4, score = 1000 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8b00 | mov eax, dword ptr [eax] // 99 | cdq // 52 | push edx $sequence_14 = { c705????????01000000 c705????????02000000 8be5 5d c3 55 } // n = 6, score = 900 // c705????????01000000 | // c705????????02000000 | // 8be5 | mov esp, ebp // 5d | pop ebp // c3 | ret // 55 | push ebp $sequence_15 = { 833d????????00 750a 6a32 ff15???????? } // n = 4, score = 800 // 833d????????00 | // 750a | jne 0xc // 6a32 | push 0x32 // ff15???????? | $sequence_16 = { 6808020000 6a00 ff15???????? 50 } // n = 4, score = 800 // 6808020000 | push 0x208 // 6a00 | push 0 // ff15???????? | // 50 | push eax $sequence_17 = { e8???????? 6a0c 6a08 ff15???????? 50 ff15???????? } // n = 6, score = 800 // e8???????? | // 6a0c | push 0xc // 6a08 | push 8 // ff15???????? | // 50 | push eax // ff15???????? | $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 = { e8???????? 85c0 750c c705????????03000000 } // n = 4, score = 500 // e8???????? | // 85c0 | test eax, eax // 750c | jne 0xe // c705????????03000000 | $sequence_20 = { 68???????? 51 51 ff15???????? 50 } // n = 5, score = 300 // 68???????? | // 51 | push ecx // 51 | push ecx // ff15???????? | // 50 | push eax $sequence_21 = { 53 53 53 8901 } // n = 4, score = 300 // 53 | push ebx // 53 | push ebx // 53 | push ebx // 8901 | mov dword ptr [ecx], eax $sequence_22 = { 50 6a01 6a0b 56 ff15???????? } // n = 5, score = 200 // 50 | push eax // 6a01 | push 1 // 6a0b | push 0xb // 56 | push esi // ff15???????? | $sequence_23 = { 0f104840 0f114730 0f104050 0f114f40 0f104860 0f114750 0f114f60 } // n = 7, score = 200 // 0f104840 | movups xmm1, xmmword ptr [eax + 0x40] // 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 $sequence_24 = { 8b36 85f6 75a2 8b3f 85ff } // n = 5, score = 200 // 8b36 | mov esi, dword ptr [esi] // 85f6 | test esi, esi // 75a2 | jne 0xffffffa4 // 8b3f | mov edi, dword ptr [edi] // 85ff | test edi, edi $sequence_25 = { 8d4864 ff15???????? ffc3 83fb0a 7cd5 33c0 } // n = 6, score = 200 // 8d4864 | lea ecx, dword ptr [eax + 0x64] // ff15???????? | // ffc3 | inc ebx // 83fb0a | cmp ebx, 0xa // 7cd5 | jl 0xffffffd7 // 33c0 | xor eax, eax $sequence_26 = { 7550 ff15???????? 8bf8 893d???????? } // n = 4, score = 200 // 7550 | jne 0x52 // ff15???????? | // 8bf8 | mov edi, eax // 893d???????? | $sequence_27 = { 0f104010 0f110f 0f104820 0f114710 0f104030 0f114f20 } // n = 6, 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 // 0f104030 | movups xmm0, xmmword ptr [eax + 0x30] // 0f114f20 | movups xmmword ptr [edi + 0x20], xmm1 $sequence_28 = { 0f104060 0f114760 8b4070 894770 be01000000 } // n = 5, 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 $sequence_29 = { a3???????? 391d???????? 7428 85c0 7424 83ec0c ba???????? } // n = 7, score = 200 // a3???????? | // 391d???????? | // 7428 | je 0x2a // 85c0 | test eax, eax // 7424 | je 0x26 // 83ec0c | sub esp, 0xc // ba???????? | $sequence_30 = { ff15???????? 85c0 7510 8d4864 ff15???????? ffc3 } // n = 6, score = 200 // ff15???????? | // 85c0 | test eax, eax // 7510 | jne 0x12 // 8d4864 | lea ecx, dword ptr [eax + 0x64] // ff15???????? | // ffc3 | inc ebx $sequence_31 = { 83faff 7508 ff15???????? 8bd0 } // n = 4, score = 200 // 83faff | cmp edx, -1 // 7508 | jne 0xa // ff15???????? | // 8bd0 | mov edx, eax $sequence_32 = { ff15???????? 8b4de8 b84d5a0000 663901 754e 8b513c } // n = 6, score = 200 // ff15???????? | // 8b4de8 | mov ecx, dword ptr [ebp - 0x18] // b84d5a0000 | mov eax, 0x5a4d // 663901 | cmp word ptr [ecx], ax // 754e | jne 0x50 // 8b513c | mov edx, dword ptr [ecx + 0x3c] $sequence_33 = { ff15???????? 8bd0 83fa01 7e18 } // n = 4, score = 200 // ff15???????? | // 8bd0 | mov edx, eax // 83fa01 | cmp edx, 1 // 7e18 | jle 0x1a $sequence_34 = { 6a10 8d45e8 50 68060000c8 56 ff15???????? } // n = 6, score = 200 // 6a10 | push 0x10 // 8d45e8 | lea eax, dword ptr [ebp - 0x18] // 50 | push eax // 68060000c8 | push 0xc8000006 // 56 | push esi // ff15???????? | condition: 7 of them and filesize < 516096 }
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