rule win_nymaim_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-09-17" version = "1" description = "Detects win.nymaim." 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.nymaim" malpedia_rule_date = "20260916" malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6" malpedia_version = "20260917" 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 = { 89d8 01c8 31d2 f7f7 } // n = 4, score = 1800 // 89d8 | mov eax, ebx // 01c8 | add eax, ecx // 31d2 | xor edx, edx // f7f7 | div edi $sequence_1 = { 92 31d2 bf64000000 f7f7 } // n = 4, score = 1700 // 92 | xchg eax, edx // 31d2 | xor edx, edx // bf64000000 | mov edi, 0x64 // f7f7 | div edi $sequence_2 = { 09c0 0f94c1 09c8 6bc064 09c0 } // n = 5, score = 1700 // 09c0 | or eax, eax // 0f94c1 | sete cl // 09c8 | or eax, ecx // 6bc064 | imul eax, eax, 0x64 // 09c0 | or eax, eax $sequence_3 = { 31d2 f7f7 92 31d2 } // n = 4, score = 1700 // 31d2 | xor edx, edx // f7f7 | div edi // 92 | xchg eax, edx // 31d2 | xor edx, edx $sequence_4 = { c1eb13 331d???????? 31c3 c1e808 } // n = 4, score = 1600 // c1eb13 | shr ebx, 0x13 // 331d???????? | // 31c3 | xor ebx, eax // c1e808 | shr eax, 8 $sequence_5 = { c1e105 01c8 c1c307 30c3 } // n = 4, score = 1600 // c1e105 | shl ecx, 5 // 01c8 | add eax, ecx // c1c307 | rol ebx, 7 // 30c3 | xor bl, al $sequence_6 = { 31c9 38f0 83d100 38d0 83d900 c1e105 01c8 } // n = 7, score = 1600 // 31c9 | xor ecx, ecx // 38f0 | cmp al, dh // 83d100 | adc ecx, 0 // 38d0 | cmp al, dl // 83d900 | sbb ecx, 0 // c1e105 | shl ecx, 5 // 01c8 | add eax, ecx $sequence_7 = { 00d3 8a16 301e 46 01fb } // n = 5, score = 1300 // 00d3 | add bl, dl // 8a16 | mov dl, byte ptr [esi] // 301e | xor byte ptr [esi], bl // 46 | inc esi // 01fb | add ebx, edi $sequence_8 = { c1e808 31c3 895e0c 89d8 } // n = 4, score = 1100 // c1e808 | shr eax, 8 // 31c3 | xor ebx, eax // 895e0c | mov dword ptr [esi + 0xc], ebx // 89d8 | mov eax, ebx $sequence_9 = { 8b5514 8b12 8b4d0c 8b5d18 } // n = 4, score = 1100 // 8b5514 | mov edx, dword ptr [ebp + 0x14] // 8b12 | mov edx, dword ptr [edx] // 8b4d0c | mov ecx, dword ptr [ebp + 0xc] // 8b5d18 | mov ebx, dword ptr [ebp + 0x18] $sequence_10 = { f7e0 0fc8 01d0 894704 } // n = 4, score = 1100 // f7e0 | mul eax // 0fc8 | bswap eax // 01d0 | add eax, edx // 894704 | mov dword ptr [edi + 4], eax $sequence_11 = { 8b5604 0116 8b4e08 014e04 } // n = 4, score = 1100 // 8b5604 | mov edx, dword ptr [esi + 4] // 0116 | add dword ptr [esi], edx // 8b4e08 | mov ecx, dword ptr [esi + 8] // 014e04 | add dword ptr [esi + 4], ecx $sequence_12 = { 8b5d18 8b1b 4f 31c0 fec2 } // n = 5, score = 1100 // 8b5d18 | mov ebx, dword ptr [ebp + 0x18] // 8b1b | mov ebx, dword ptr [ebx] // 4f | dec edi // 31c0 | xor eax, eax // fec2 | inc dl $sequence_13 = { 0f854fe70000 448835???????? 015308 395320 0f845a13fdff f6461c20 c705????????8a50d8e8 } // n = 7, score = 100 // 0f854fe70000 | lea ecx, [ebp - 0x10] // 448835???????? | // 015308 | dec eax // 395320 | mov edx, dword ptr [ebp + 0x500] // 0f845a13fdff | inc esp // f6461c20 | mov edx, dword ptr [ebp + 0x4e0] // c705????????8a50d8e8 | $sequence_14 = { 55 89e5 83ec10 8b4508 8d0d3430d201 } // n = 5, score = 100 // 55 | push ebp // 89e5 | mov ebp, esp // 83ec10 | sub esp, 0x10 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8d0d3430d201 | lea ecx, [0x1d23034] $sequence_15 = { 890424 894c2404 e8???????? 8d0d3430d201 } // n = 4, score = 100 // 890424 | mov dword ptr [esp], eax // 894c2404 | mov dword ptr [esp + 4], ecx // e8???????? | // 8d0d3430d201 | lea ecx, [0x1d23034] $sequence_16 = { 4189c6 892d???????? 4189f9 4189d8 4489f1 8b8424c8000000 89ea } // n = 7, score = 100 // 4189c6 | mov ecx, edi // 892d???????? | // 4189f9 | mov edx, esi // 4189d8 | mov ecx, ebp // 4489f1 | inc ecx // 8b8424c8000000 | mov esi, eax // 89ea | inc ecx $sequence_17 = { 5b 5d c3 8b45f0 8b0c850440d201 } // n = 5, score = 100 // 5b | pop ebx // 5d | pop ebp // c3 | ret // 8b45f0 | mov eax, dword ptr [ebp - 0x10] // 8b0c850440d201 | mov ecx, dword ptr [eax*4 + 0x1d24004] $sequence_18 = { 448b4d30 4189c3 4531d3 66813d????????65cb 0f8484920200 41f7d1 4531c8 } // n = 7, score = 100 // 448b4d30 | lea ecx, [esp + 0x40] // 4189c3 | dec ecx // 4531d3 | mov ebx, esp // 66813d????????65cb | // 0f8484920200 | push ebx // 41f7d1 | je 0x19 // 4531c8 | dec eax $sequence_19 = { 48833d????????00 7417 488d4df0 e8???????? 488b9500050000 448b95e0040000 31db } // n = 7, score = 100 // 48833d????????00 | // 7417 | mov ecx, esi // 488d4df0 | mov eax, dword ptr [esp + 0xc8] // e8???????? | // 488b9500050000 | mov edx, ebp // 448b95e0040000 | ja 0xfffe5975 // 31db | dec eax $sequence_20 = { 48813d????????00000050 0f84b243ffff 48c705????????00000000 31ff 4883bba800000000 742b ba20000000 } // n = 7, score = 100 // 48813d????????00000050 | // 0f84b243ffff | je 0xffff43b8 // 48c705????????00000000 | // 31ff | xor edi, edi // 4883bba800000000 | dec eax // 742b | cmp dword ptr [ebx + 0xa8], 0 // ba20000000 | je 0x2d $sequence_21 = { 56 83ec28 8b450c 8b4d08 8d154e30d201 } // n = 5, score = 100 // 56 | push esi // 83ec28 | sub esp, 0x28 // 8b450c | mov eax, dword ptr [ebp + 0xc] // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 8d154e30d201 | lea edx, [0x1d2304e] $sequence_22 = { 31c9 8b55f4 8b75ec 89723c c7424003000000 } // n = 5, score = 100 // 31c9 | xor ecx, ecx // 8b55f4 | mov edx, dword ptr [ebp - 0xc] // 8b75ec | mov esi, dword ptr [ebp - 0x14] // 89723c | mov dword ptr [edx + 0x3c], esi // c7424003000000 | mov dword ptr [edx + 0x40], 3 $sequence_23 = { 4421db 89c2 4409d2 4431ca 4c8d4d40 48ff05???????? 89d1 } // n = 7, score = 100 // 4421db | xor ebx, ebx // 89c2 | inc esp // 4409d2 | mov ecx, dword ptr [ebp + 0x30] // 4431ca | inc ecx // 4c8d4d40 | mov ebx, eax // 48ff05???????? | // 89d1 | inc ebp $sequence_24 = { 31d2 890c24 c744240400000000 8945f4 8955f0 e8???????? 8d0d8630d201 } // n = 7, score = 100 // 31d2 | xor edx, edx // 890c24 | mov dword ptr [esp], ecx // c744240400000000 | mov dword ptr [esp + 4], 0 // 8945f4 | mov dword ptr [ebp - 0xc], eax // 8955f0 | mov dword ptr [ebp - 0x10], edx // e8???????? | // 8d0d8630d201 | lea ecx, [0x1d23086] $sequence_25 = { 83ec44 8b4508 8d0d2030d201 31d2 890c24 c744240400000000 } // n = 6, score = 100 // 83ec44 | sub esp, 0x44 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8d0d2030d201 | lea ecx, [0x1d23020] // 31d2 | xor edx, edx // 890c24 | mov dword ptr [esp], ecx // c744240400000000 | mov dword ptr [esp + 4], 0 $sequence_26 = { 53 56 57 83ec44 8b4508 8d0d2030d201 } // n = 6, score = 100 // 53 | push ebx // 56 | push esi // 57 | push edi // 83ec44 | sub esp, 0x44 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8d0d2030d201 | lea ecx, [0x1d23020] $sequence_27 = { 0f876f59feff 488d4c2440 e8???????? e9???????? 4989e3 53 ff0d???????? } // n = 7, score = 100 // 0f876f59feff | mov ecx, edi // 488d4c2440 | inc ecx // e8???????? | // e9???????? | // 4989e3 | mov eax, ebx // 53 | inc esp // ff0d???????? | $sequence_28 = { 4189c0 895c2420 4189f9 48890d???????? 89f2 89e9 e8???????? } // n = 7, score = 100 // 4189c0 | mov edx, 0x20 // 895c2420 | inc ecx // 4189f9 | mov eax, eax // 48890d???????? | // 89f2 | mov dword ptr [esp + 0x20], ebx // 89e9 | inc ecx // e8???????? | condition: 1 of them and filesize < 2375680 }