rule win_cryptbot_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-09-17" version = "1" description = "Detects win.cryptbot." 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.cryptbot" malpedia_rule_date = "20260916" malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6" malpedia_version = "20260917" 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 = { 85c0 750e b9ca070200 e8???????? 8bc8 } // n = 5, score = 600 // 85c0 | test eax, eax // 750e | jne 0x10 // b9ca070200 | mov ecx, 0x207ca // e8???????? | // 8bc8 | mov ecx, eax $sequence_1 = { 895804 e8???????? c74004d0070000 e9???????? } // n = 4, score = 600 // 895804 | mov dword ptr [eax + 4], ebx // e8???????? | // c74004d0070000 | mov dword ptr [eax + 4], 0x7d0 // e9???????? | $sequence_2 = { 33c0 eb0a b917d90000 e8???????? } // n = 4, score = 600 // 33c0 | xor eax, eax // eb0a | jmp 0xc // b917d90000 | mov ecx, 0xd917 // e8???????? | $sequence_3 = { 84c0 7514 b800000002 e9???????? } // n = 4, score = 600 // 84c0 | test al, al // 7514 | jne 0x16 // b800000002 | mov eax, 0x2000000 // e9???????? | $sequence_4 = { 85c0 740a b9491a0100 e9???????? } // n = 4, score = 600 // 85c0 | test eax, eax // 740a | je 0xc // b9491a0100 | mov ecx, 0x11a49 // e9???????? | $sequence_5 = { 85f6 790e b9e2d80000 e8???????? 8907 } // n = 5, score = 600 // 85f6 | test esi, esi // 790e | jns 0x10 // b9e2d80000 | mov ecx, 0xd8e2 // e8???????? | // 8907 | mov dword ptr [edi], eax $sequence_6 = { 85c0 750f b955960100 e8???????? e9???????? } // n = 5, score = 600 // 85c0 | test eax, eax // 750f | jne 0x11 // b955960100 | mov ecx, 0x19655 // e8???????? | // e9???????? | $sequence_7 = { 83f8ff 7407 c1e804 2401 8ad8 8ac3 } // n = 6, score = 600 // 83f8ff | cmp eax, -1 // 7407 | je 9 // c1e804 | shr eax, 4 // 2401 | and al, 1 // 8ad8 | mov bl, al // 8ac3 | mov al, bl $sequence_8 = { 7411 ffb6c4000000 6a00 50 e8???????? 83c40c 8bce } // n = 7, score = 400 // 7411 | je 0x13 // ffb6c4000000 | push dword ptr [esi + 0xc4] // 6a00 | push 0 // 50 | push eax // e8???????? | // 83c40c | add esp, 0xc // 8bce | mov ecx, esi $sequence_9 = { 7518 8b542414 83c718 8bcd } // n = 4, score = 400 // 7518 | jne 0x1a // 8b542414 | mov edx, dword ptr [esp + 0x14] // 83c718 | add edi, 0x18 // 8bcd | mov ecx, ebp $sequence_10 = { 83caff 8bcf e8???????? 83caff } // n = 4, score = 400 // 83caff | or edx, 0xffffffff // 8bcf | mov ecx, edi // e8???????? | // 83caff | or edx, 0xffffffff $sequence_11 = { 7424 807e4100 7404 33c0 } // n = 4, score = 400 // 7424 | je 0x26 // 807e4100 | cmp byte ptr [esi + 0x41], 0 // 7404 | je 6 // 33c0 | xor eax, eax $sequence_12 = { 750f 8a44245c 84c0 7507 } // n = 4, score = 400 // 750f | jne 0x11 // 8a44245c | mov al, byte ptr [esp + 0x5c] // 84c0 | test al, al // 7507 | jne 9 $sequence_13 = { 7510 83be9c01000000 7507 8bce } // n = 4, score = 400 // 7510 | jne 0x12 // 83be9c01000000 | cmp dword ptr [esi + 0x19c], 0 // 7507 | jne 9 // 8bce | mov ecx, esi $sequence_14 = { 85c0 742c 8bd6 8bcb } // n = 4, score = 400 // 85c0 | test eax, eax // 742c | je 0x2e // 8bd6 | mov edx, esi // 8bcb | mov ecx, ebx $sequence_15 = { 741e 8b491c 8b442434 803c0800 7411 33c0 39442438 } // n = 7, score = 400 // 741e | je 0x20 // 8b491c | mov ecx, dword ptr [ecx + 0x1c] // 8b442434 | mov eax, dword ptr [esp + 0x34] // 803c0800 | cmp byte ptr [eax + ecx], 0 // 7411 | je 0x13 // 33c0 | xor eax, eax // 39442438 | cmp dword ptr [esp + 0x38], eax $sequence_16 = { 750b 8bce e8???????? 8b4c2428 } // n = 4, score = 400 // 750b | jne 0xd // 8bce | mov ecx, esi // e8???????? | // 8b4c2428 | mov ecx, dword ptr [esp + 0x28] $sequence_17 = { 744e 0fb74802 83e103 3bcb } // n = 4, score = 400 // 744e | je 0x50 // 0fb74802 | movzx ecx, word ptr [eax + 2] // 83e103 | and ecx, 3 // 3bcb | cmp ecx, ebx $sequence_18 = { 8b5720 8bce e8???????? 8b5724 } // n = 4, score = 200 // 8b5720 | mov edx, dword ptr [edi + 0x20] // 8bce | mov ecx, esi // e8???????? | // 8b5724 | mov edx, dword ptr [edi + 0x24] $sequence_19 = { 8b4d18 8901 895104 e9???????? 8b4508 } // n = 5, score = 100 // 8b4d18 | mov ecx, dword ptr [ebp + 0x18] // 8901 | mov dword ptr [ecx], eax // 895104 | mov dword ptr [ecx + 4], edx // e9???????? | // 8b4508 | mov eax, dword ptr [ebp + 8] $sequence_20 = { 8b4d20 894c2468 8b4d5c 894c2464 } // n = 4, score = 100 // 8b4d20 | mov ecx, dword ptr [ebp + 0x20] // 894c2468 | mov dword ptr [esp + 0x68], ecx // 8b4d5c | mov ecx, dword ptr [ebp + 0x5c] // 894c2464 | mov dword ptr [esp + 0x64], ecx $sequence_21 = { 8b95acfeffff 33c0 3802 7406 } // n = 4, score = 100 // 8b95acfeffff | mov edx, dword ptr [ebp - 0x154] // 33c0 | xor eax, eax // 3802 | cmp byte ptr [edx], al // 7406 | je 8 $sequence_22 = { 8b959cfeffff 8bca 85d2 742a } // n = 4, score = 100 // 8b959cfeffff | mov edx, dword ptr [ebp - 0x164] // 8bca | mov ecx, edx // 85d2 | test edx, edx // 742a | je 0x2c $sequence_23 = { 8b4d18 8b09 81c1fc030000 8b448808 } // n = 4, score = 100 // 8b4d18 | mov ecx, dword ptr [ebp + 0x18] // 8b09 | mov ecx, dword ptr [ecx] // 81c1fc030000 | add ecx, 0x3fc // 8b448808 | mov eax, dword ptr [eax + ecx*4 + 8] $sequence_24 = { 8b95a0feffff 6a00 6a00 8b08 } // n = 4, score = 100 // 8b95a0feffff | mov edx, dword ptr [ebp - 0x160] // 6a00 | push 0 // 6a00 | push 0 // 8b08 | mov ecx, dword ptr [eax] $sequence_25 = { 8b959cfeffff 8b85acfeffff 33c9 3808 } // n = 4, score = 100 // 8b959cfeffff | mov edx, dword ptr [ebp - 0x164] // 8b85acfeffff | mov eax, dword ptr [ebp - 0x154] // 33c9 | xor ecx, ecx // 3808 | cmp byte ptr [eax], cl $sequence_26 = { 8b4d34 894c245c dd85b8fbffff dd5c2454 } // n = 4, score = 100 // 8b4d34 | mov ecx, dword ptr [ebp + 0x34] // 894c245c | mov dword ptr [esp + 0x5c], ecx // dd85b8fbffff | fld qword ptr [ebp - 0x448] // dd5c2454 | fstp qword ptr [esp + 0x54] $sequence_27 = { 8b4d18 8b09 83c101 81c1fc030000 } // n = 4, score = 100 // 8b4d18 | mov ecx, dword ptr [ebp + 0x18] // 8b09 | mov ecx, dword ptr [ecx] // 83c101 | add ecx, 1 // 81c1fc030000 | add ecx, 0x3fc $sequence_28 = { 8b4d24 894c247c dd85b0fbffff dd5c2474 } // n = 4, score = 100 // 8b4d24 | mov ecx, dword ptr [ebp + 0x24] // 894c247c | mov dword ptr [esp + 0x7c], ecx // dd85b0fbffff | fld qword ptr [ebp - 0x450] // dd5c2474 | fstp qword ptr [esp + 0x74] $sequence_29 = { 8b4d34 894c2470 8b4d64 894c246c } // n = 4, score = 100 // 8b4d34 | mov ecx, dword ptr [ebp + 0x34] // 894c2470 | mov dword ptr [esp + 0x70], ecx // 8b4d64 | mov ecx, dword ptr [ebp + 0x64] // 894c246c | mov dword ptr [esp + 0x6c], ecx $sequence_30 = { 8b4d28 898d30ffffff 8b958c000000 89952cffffff } // n = 4, score = 100 // 8b4d28 | mov ecx, dword ptr [ebp + 0x28] // 898d30ffffff | mov dword ptr [ebp - 0xd0], ecx // 8b958c000000 | mov edx, dword ptr [ebp + 0x8c] // 89952cffffff | mov dword ptr [ebp - 0xd4], edx $sequence_31 = { 8b958cfeffff 2bc2 8bb5a0feffff 03f0 8a02 } // n = 5, score = 100 // 8b958cfeffff | mov edx, dword ptr [ebp - 0x174] // 2bc2 | sub eax, edx // 8bb5a0feffff | mov esi, dword ptr [ebp - 0x160] // 03f0 | add esi, eax // 8a02 | mov al, byte ptr [edx] condition: 7 of them and filesize < 17138688 }