Actor(s): Lazarus Group
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rule win_wannacryptor_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2020-12-22" version = "1" description = "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.wannacryptor" malpedia_rule_date = "20201222" malpedia_hash = "30354d830a29f0fbd3714d93d94dea941d77a130" malpedia_version = "20201023" 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 = { 83ec1c 56 8bf1 8a465a 84c0 756f 8a4658 } // n = 7, score = 600 // 83ec1c | sub esp, 0x1c // 56 | push esi // 8bf1 | mov esi, ecx // 8a465a | mov al, byte ptr [esi + 0x5a] // 84c0 | test al, al // 756f | jne 0x71 // 8a4658 | mov al, byte ptr [esi + 0x58] $sequence_1 = { 5d 5b 81c410040000 c21000 8bb42424040000 } // n = 5, score = 600 // 5d | pop ebp // 5b | pop ebx // 81c410040000 | add esp, 0x410 // c21000 | ret 0x10 // 8bb42424040000 | mov esi, dword ptr [esp + 0x424] $sequence_2 = { 83c408 89442430 8d442428 8d4c2430 50 51 8954243c } // n = 7, score = 600 // 83c408 | add esp, 8 // 89442430 | mov dword ptr [esp + 0x30], eax // 8d442428 | lea eax, [esp + 0x28] // 8d4c2430 | lea ecx, [esp + 0x30] // 50 | push eax // 51 | push ecx // 8954243c | mov dword ptr [esp + 0x3c], edx $sequence_3 = { 8bce e8???????? 8a4649 84c0 7419 8b4620 } // n = 6, score = 600 // 8bce | mov ecx, esi // e8???????? | // 8a4649 | mov al, byte ptr [esi + 0x49] // 84c0 | test al, al // 7419 | je 0x1b // 8b4620 | mov eax, dword ptr [esi + 0x20] $sequence_4 = { 33ff 85c0 7e2b 8bd8 8b5500 03cf 8a4411ff } // n = 7, score = 600 // 33ff | xor edi, edi // 85c0 | test eax, eax // 7e2b | jle 0x2d // 8bd8 | mov ebx, eax // 8b5500 | mov edx, dword ptr [ebp] // 03cf | add ecx, edi // 8a4411ff | mov al, byte ptr [ecx + edx - 1] $sequence_5 = { 83fa01 0f850f010000 38564b 7526 8b4644 } // n = 5, score = 600 // 83fa01 | cmp edx, 1 // 0f850f010000 | jne 0x115 // 38564b | cmp byte ptr [esi + 0x4b], dl // 7526 | jne 0x28 // 8b4644 | mov eax, dword ptr [esi + 0x44] $sequence_6 = { b907000000 33c0 8d7e08 c74604ffffffff f3ab 66ab } // n = 6, score = 600 // b907000000 | mov ecx, 7 // 33c0 | xor eax, eax // 8d7e08 | lea edi, [esi + 8] // c74604ffffffff | mov dword ptr [esi + 4], 0xffffffff // f3ab | rep stosd dword ptr es:[edi], eax // 66ab | stosw word ptr es:[edi], ax $sequence_7 = { e8???????? 8b0e 8bf8 8b442414 897c241c } // n = 5, score = 600 // e8???????? | // 8b0e | mov ecx, dword ptr [esi] // 8bf8 | mov edi, eax // 8b442414 | mov eax, dword ptr [esp + 0x14] // 897c241c | mov dword ptr [esp + 0x1c], edi $sequence_8 = { e8???????? 8bf8 8b4640 8d542408 8b48f8 52 51 } // n = 7, score = 600 // e8???????? | // 8bf8 | mov edi, eax // 8b4640 | mov eax, dword ptr [esi + 0x40] // 8d542408 | lea edx, [esp + 8] // 8b48f8 | mov ecx, dword ptr [eax - 8] // 52 | push edx // 51 | push ecx $sequence_9 = { 8d4c2420 b306 50 51 } // n = 4, score = 600 // 8d4c2420 | lea ecx, [esp + 0x20] // b306 | mov bl, 6 // 50 | push eax // 51 | push ecx condition: 7 of them and filesize < 540672 }
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