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rule win_nokoyawa_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.nokoyawa." 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.nokoyawa" malpedia_rule_date = "20231130" malpedia_hash = "fc8a0e9f343f6d6ded9e7df1a64dac0cc68d7351" malpedia_version = "20230808" 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 = { 33c8 8bc1 8b4c2420 488b9424c0000000 88040a e9???????? 33c0 } // n = 7, score = 100 // 33c8 | dec eax // 8bc1 | mov edx, eax // 8b4c2420 | xor ecx, ecx // 488b9424c0000000 | add ecx, 4 // 88040a | dec eax // e9???????? | // 33c0 | arpl cx, cx $sequence_1 = { 488b4c2460 e8???????? 488b442468 4883e0c0 } // n = 4, score = 100 // 488b4c2460 | dec eax // e8???????? | // 488b442468 | mov dword ptr [esp + 0x10], eax // 4883e0c0 | cmp dword ptr [esp], 3 $sequence_2 = { 890424 8b0424 83c003 99 83e203 03c2 c1f802 } // n = 7, score = 100 // 890424 | mov eax, 4 // 8b0424 | shl eax, 1 // 83c003 | mov ecx, dword ptr [esp] // 99 | shr ecx, 0x1f // 83e203 | or eax, ecx // 03c2 | mov dword ptr [esp + 0x134], eax // c1f802 | mov eax, 4 $sequence_3 = { 488b4c2448 488b0c01 e8???????? 85c0 7511 c605????????01 e8???????? } // n = 7, score = 100 // 488b4c2448 | mov ecx, dword ptr [esp + 0x164] // 488b0c01 | mov dword ptr [esp + eax + 0x20], ecx // e8???????? | // 85c0 | mov eax, dword ptr [esp + 0x10] // 7511 | mov ecx, dword ptr [esp + 0xc] // c605????????01 | // e8???????? | $sequence_4 = { 89442434 e8???????? 488905???????? 8b442434 } // n = 4, score = 100 // 89442434 | movzx eax, byte ptr [ecx + eax] // e8???????? | // 488905???????? | // 8b442434 | shl eax, 2 $sequence_5 = { 48894c2408 4883ec18 48c7042400000000 488b442420 488b0c24 0fb70448 } // n = 6, score = 100 // 48894c2408 | mov ecx, edx // 4883ec18 | or ecx, eax // 48c7042400000000 | mov eax, ecx // 488b442420 | mov ecx, dword ptr [esp + 4] // 488b0c24 | shr ecx, 0x1b // 0fb70448 | mov ecx, edx $sequence_6 = { 8b442420 83c014 89442420 837c242040 } // n = 4, score = 100 // 8b442420 | dec eax // 83c014 | add esp, 0x48 // 89442420 | dec eax // 837c242040 | mov dword ptr [esp + 0x30], 0 $sequence_7 = { 880424 488b442410 48c1e005 4803442410 0fb60c24 4803c1 4889442410 } // n = 7, score = 100 // 880424 | mov ecx, 0xffffffff // 488b442410 | inc ecx // 48c1e005 | mov eax, 1 // 4803442410 | mov ecx, eax // 0fb60c24 | shl eax, 1 // 4803c1 | dec eax // 4889442410 | cwde $sequence_8 = { 486bc907 8b4c0c20 8b440420 33c1 b904000000 } // n = 5, score = 100 // 486bc907 | lea ecx, [0x74d9] // 8b4c0c20 | dec eax // 8b440420 | cwde // 33c1 | dec eax // b904000000 | lea edx, [0x650b] $sequence_9 = { 8b9424a0000000 03d1 8bca 8d8408a1ebd96e 8b4c2414 03c8 } // n = 6, score = 100 // 8b9424a0000000 | mov eax, 0x80 // 03d1 | dec eax // 8bca | sub eax, dword ptr [esp + 0x30] // 8d8408a1ebd96e | dec eax // 8b4c2414 | mov dword ptr [esp + 0x38], eax // 03c8 | dec eax condition: 7 of them and filesize < 92160 }
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