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rule win_nokoyawa_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" 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 = "20220513" malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26" malpedia_version = "20220516" 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 = { 41b801000000 488d542428 488d4c2428 e8???????? bae9000000 488d4c2428 e8???????? } // n = 7, score = 100 // 41b801000000 | mov edx, 0x40 // 488d542428 | dec eax // 488d4c2428 | lea ecx, [esp + 0x50] // e8???????? | // bae9000000 | dec esp // 488d4c2428 | lea eax, [esp + 0x130] // e8???????? | $sequence_1 = { 0bd1 8bca 8b9424e4000000 03d1 } // n = 4, score = 100 // 0bd1 | or edx, ecx // 8bca | mov ecx, edx // 8b9424e4000000 | mov edx, dword ptr [esp + 0x150] // 03d1 | add edx, ecx $sequence_2 = { 817c244403010000 7402 eb0e 817c244403010000 0f850fffffff 488b4c2438 } // n = 6, score = 100 // 817c244403010000 | dec eax // 7402 | mov ecx, dword ptr [esp + 0x40] // eb0e | mov ecx, dword ptr [ecx] // 817c244403010000 | add eax, dword ptr [ecx] // 0f850fffffff | mov edx, 0xd // 488b4c2438 | mov ecx, eax $sequence_3 = { e9???????? 8b442440 448bc0 33d2 488b4c2438 e8???????? } // n = 6, score = 100 // e9???????? | // 8b442440 | mov eax, dword ptr [esp + 0x40] // 448bc0 | dec eax // 33d2 | mov ecx, dword ptr [esp + 0x50] // 488b4c2438 | dec eax // e8???????? | $sequence_4 = { 894c0420 8b442404 8b4c2414 0bc8 8bc1 8b4c2408 23c8 } // n = 7, score = 100 // 894c0420 | shr ecx, 0x1f // 8b442404 | or eax, ecx // 8b4c2414 | mov dword ptr [esp + 0xb4], eax // 0bc8 | mov eax, 4 // 8bc1 | dec eax // 8b4c2408 | imul eax, eax, 3 // 23c8 | mov ecx, dword ptr [esp + 0xb4] $sequence_5 = { 81e100ff0000 0bc1 488b4c2468 8b09 c1e918 } // n = 5, score = 100 // 81e100ff0000 | inc esp // 0bc1 | mov eax, dword ptr [esp + 0x20] // 488b4c2468 | dec eax // 8b09 | imul eax, eax, 0x30 // c1e918 | dec eax $sequence_6 = { 8b4c2408 03c8 8bc1 89442408 8b442410 } // n = 5, score = 100 // 8b4c2408 | cmp dword ptr [esp + 8], 0x3f // 03c8 | jg 0xd90 // 8bc1 | dec eax // 89442408 | mov eax, dword ptr [esp + 0x20] // 8b442410 | movzx eax, word ptr [eax] $sequence_7 = { b808000000 486bc001 488d15fb700000 488b4c2448 488b0c01 e8???????? } // n = 6, score = 100 // b808000000 | dec eax // 486bc001 | mov dword ptr [esp + 8], eax // 488d15fb700000 | dec eax // 488b4c2448 | mov eax, dword ptr [esp + 0x38] // 488b0c01 | dec eax // e8???????? | $sequence_8 = { 33c0 85c0 0f8528ffffff b804000000 486bc00a } // n = 5, score = 100 // 33c0 | dec eax // 85c0 | mov ecx, dword ptr [esp + 0x48] // 0f8528ffffff | mov eax, 0x43 // b804000000 | mov word ptr [esp + 0x20], ax // 486bc00a | jmp 0x1769 $sequence_9 = { eb6f c644242201 c644242101 0fb6442420 85c0 7424 8b442424 } // n = 7, score = 100 // eb6f | dec eax // c644242201 | mov eax, dword ptr [esp + 0x10] // c644242101 | dec eax // 0fb6442420 | add eax, 2 // 85c0 | dec eax // 7424 | sub eax, 4 // 8b442424 | dec eax condition: 7 of them and filesize < 92160 }
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