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rule win_revc2_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.revc2." 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.revc2" malpedia_rule_date = "20260105" malpedia_hash = "19b79e7cab4eaf532122e5b45a77dd8f6bb5cc79" malpedia_version = "20251219" 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 = { 8d4701 458bca 458bec 0f45f8 be01000000 8364244000 4183e21f } // n = 7, score = 100 // 8d4701 | dec eax // 458bca | mov ecx, dword ptr [ecx + 0x28] // 458bec | inc esp // 0f45f8 | mov ecx, eax // be01000000 | mov eax, edx // 8364244000 | inc ecx // 4183e21f | and eax, ebx $sequence_1 = { e8???????? 498946b0 488bc3 49894500 486307 4c6bf068 410fb6842434010000 } // n = 7, score = 100 // e8???????? | // 498946b0 | dec eax // 488bc3 | mov ebx, eax // 49894500 | dec eax // 486307 | lea edx, [0x1f28bb] // 4c6bf068 | dec eax // 410fb6842434010000 | lea ecx, [esp + 0x30] $sequence_2 = { 90 488d8d90000000 e8???????? 90 488d4dd0 e8???????? 90 } // n = 7, score = 100 // 90 | lea eax, [ecx + 1] // 488d8d90000000 | xor edx, edx // e8???????? | // 90 | mov dword ptr [ebx + 0x90], eax // 488d4dd0 | dec eax // e8???????? | // 90 | lea ecx, [ecx + ecx*2] $sequence_3 = { ff15???????? e9???????? 488b0e 488b11 0fb74214 a804 0f84ab010000 } // n = 7, score = 100 // ff15???????? | // e9???????? | // 488b0e | and ecx, edx // 488b11 | inc esp // 0fb74214 | lea eax, [edx - 0x275e197f] // a804 | inc ecx // 0f84ab010000 | and eax, edx $sequence_4 = { c5fe6f27 c5fe6f15???????? c5fe6f2d???????? c5fd71d404 c5fddbca c4e24d00d9 c5eddbc4 } // n = 7, score = 100 // c5fe6f27 | mov ecx, dword ptr [ebp + 0x130] // c5fe6f15???????? | // c5fe6f2d???????? | // c5fd71d404 | mov edi, 0x8007000e // c5fddbca | mov ecx, eax // c4e24d00d9 | test eax, eax // c5eddbc4 | je 0x1533 $sequence_5 = { eb12 4863c6 488d0c40 488b8388000000 488d04c8 895008 418d7701 } // n = 7, score = 100 // eb12 | mov ebx, dword ptr [esp + 0x48] // 4863c6 | dec ecx // 488d0c40 | mov ecx, dword ptr [ebx] // 488b8388000000 | jmp 0x99 // 488d04c8 | inc ecx // 895008 | mov ecx, dword ptr [ebx + ebx*4 + 0x1f25e0] // 418d7701 | cmp dword ptr [esp + 0x70], 5 $sequence_6 = { e8???????? 4c8b8424b8000000 498b38 4885ff 0f84fa010000 418bdd 4c8d0dca611200 } // n = 7, score = 100 // e8???????? | // 4c8b8424b8000000 | lea eax, [0x1fbe15] // 498b38 | dec eax // 4885ff | mov dword ptr [esp + 0x58], eax // 0f84fa010000 | dec eax // 418bdd | mov ecx, dword ptr [edi + 0x38] // 4c8d0dca611200 | dec eax $sequence_7 = { 4c894dc0 4889542450 4889442458 4c895c2440 895c2430 895c2470 895da0 } // n = 7, score = 100 // 4c894dc0 | mov dword ptr [ebp + edx*8], eax // 4889542450 | dec edx // 4889442458 | mov eax, dword ptr [ebp + ebp*8 - 8] // 4c895c2440 | dec eax // 895c2430 | mov dword ptr [ebp + edx*8 + 8], eax // 895c2470 | dec esp // 895da0 | cmp edi, ebx $sequence_8 = { e8???????? 90 4c8bc0 488d4d50 e8???????? 488bf8 488d542450 } // n = 7, score = 100 // e8???????? | // 90 | inc esp // 4c8bc0 | mov ecx, edx // 488d4d50 | mov edx, dword ptr [esp + 0x40] // e8???????? | // 488bf8 | jmp 0xd21 // 488d542450 | mov edx, dword ptr [esp + 0x40] $sequence_9 = { e8???????? 488bc3 488b5c2450 488b7c2458 4883c440 5d c3 } // n = 7, score = 100 // e8???????? | // 488bc3 | mov ecx, dword ptr [edi + 0x18] // 488b5c2450 | movzx ebx, al // 488b7c2458 | dec eax // 4883c440 | test ecx, ecx // 5d | je 0x260 // c3 | movzx ecx, al condition: 7 of them and filesize < 5108736 }
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