Actor(s): Lazarus Group
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rule win_wannacryptor_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.wannacryptor." 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.wannacryptor" malpedia_rule_date = "20230705" malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41" malpedia_version = "20230715" 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 = { c744244817406700 894c244c 896c2450 89542454 } // n = 4, score = 600 // c744244817406700 | mov dword ptr [esp + 0x48], 0x674017 // 894c244c | mov dword ptr [esp + 0x4c], ecx // 896c2450 | mov dword ptr [esp + 0x50], ebp // 89542454 | mov dword ptr [esp + 0x54], edx $sequence_1 = { 55 8be9 8b8c2444020000 56 57 51 c744241401000000 } // n = 7, score = 600 // 55 | push ebp // 8be9 | mov ebp, ecx // 8b8c2444020000 | mov ecx, dword ptr [esp + 0x244] // 56 | push esi // 57 | push edi // 51 | push ecx // c744241401000000 | mov dword ptr [esp + 0x14], 1 $sequence_2 = { 8bf0 8975dc 83feff 750a 50 8d55f0 52 } // n = 7, score = 600 // 8bf0 | mov esi, eax // 8975dc | mov dword ptr [ebp - 0x24], esi // 83feff | cmp esi, -1 // 750a | jne 0xc // 50 | push eax // 8d55f0 | lea edx, [ebp - 0x10] // 52 | push edx $sequence_3 = { 56 51 57 ffd5 85c0 7418 8a442413 } // n = 7, score = 600 // 56 | push esi // 51 | push ecx // 57 | push edi // ffd5 | call ebp // 85c0 | test eax, eax // 7418 | je 0x1a // 8a442413 | mov al, byte ptr [esp + 0x13] $sequence_4 = { 8bce e8???????? 85db 7403 8b5b04 } // n = 5, score = 600 // 8bce | mov ecx, esi // e8???????? | // 85db | test ebx, ebx // 7403 | je 5 // 8b5b04 | mov ebx, dword ptr [ebx + 4] $sequence_5 = { ff15???????? 50 e8???????? 85c0 742e 8b4004 8d542404 } // n = 7, score = 600 // ff15???????? | // 50 | push eax // e8???????? | // 85c0 | test eax, eax // 742e | je 0x30 // 8b4004 | mov eax, dword ptr [eax + 4] // 8d542404 | lea edx, [esp + 4] $sequence_6 = { f7f9 85c0 7443 3bf9 7c3f } // n = 5, score = 600 // f7f9 | idiv ecx // 85c0 | test eax, eax // 7443 | je 0x45 // 3bf9 | cmp edi, ecx // 7c3f | jl 0x41 $sequence_7 = { 51 8954243c ff15???????? 8b442428 8b4c242c } // n = 5, score = 600 // 51 | push ecx // 8954243c | mov dword ptr [esp + 0x3c], edx // ff15???????? | // 8b442428 | mov eax, dword ptr [esp + 0x28] // 8b4c242c | mov ecx, dword ptr [esp + 0x2c] $sequence_8 = { 57 837d0000 0f85d2000000 837d04ff 0f85c8000000 53 8d9d40010000 } // n = 7, score = 600 // 57 | push edi // 837d0000 | cmp dword ptr [ebp], 0 // 0f85d2000000 | jne 0xd8 // 837d04ff | cmp dword ptr [ebp + 4], -1 // 0f85c8000000 | jne 0xce // 53 | push ebx // 8d9d40010000 | lea ebx, [ebp + 0x140] $sequence_9 = { 894204 8b4e0c 3bcb 741e 8a41ff 3ac3 } // n = 6, score = 600 // 894204 | mov dword ptr [edx + 4], eax // 8b4e0c | mov ecx, dword ptr [esi + 0xc] // 3bcb | cmp ecx, ebx // 741e | je 0x20 // 8a41ff | mov al, byte ptr [ecx - 1] // 3ac3 | cmp al, bl condition: 7 of them and filesize < 540672 }
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