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rule win_polyglot_ransom_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.polyglot_ransom." 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.polyglot_ransom" malpedia_rule_date = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" 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 = { 8bf0 83e61f 8d3c8d809b4800 8b0f c1e606 833c0eff 7536 } // n = 7, score = 100 // 8bf0 | mov esi, eax // 83e61f | and esi, 0x1f // 8d3c8d809b4800 | lea edi, [ecx*4 + 0x489b80] // 8b0f | mov ecx, dword ptr [edi] // c1e606 | shl esi, 6 // 833c0eff | cmp dword ptr [esi + ecx], -1 // 7536 | jne 0x38 $sequence_1 = { 80d0b5 d182d0bdd0be d0b3d0be20d0 bad0bbd18e d187d0b020d0 bdd0b520d0 b2d0 } // n = 7, score = 100 // 80d0b5 | adc al, 0xb5 // d182d0bdd0be | rol dword ptr [edx - 0x412f4230], 1 // d0b3d0be20d0 | sal byte ptr [ebx - 0x2fdf4130], 1 // bad0bbd18e | mov edx, 0x8ed1bbd0 // d187d0b020d0 | rol dword ptr [edi - 0x2fdf4f30], 1 // bdd0b520d0 | mov ebp, 0xd020b5d0 // b2d0 | mov dl, 0xd0 $sequence_2 = { 8b7e04 85ff 741e 8b4e08 8b4108 53 8b1f } // n = 7, score = 100 // 8b7e04 | mov edi, dword ptr [esi + 4] // 85ff | test edi, edi // 741e | je 0x20 // 8b4e08 | mov ecx, dword ptr [esi + 8] // 8b4108 | mov eax, dword ptr [ecx + 8] // 53 | push ebx // 8b1f | mov ebx, dword ptr [edi] $sequence_3 = { a900000100 74c6 5f 5e 8bc3 5b c20800 } // n = 7, score = 100 // a900000100 | test eax, 0x10000 // 74c6 | je 0xffffffc8 // 5f | pop edi // 5e | pop esi // 8bc3 | mov eax, ebx // 5b | pop ebx // c20800 | ret 8 $sequence_4 = { c9 c3 53 56 57 68???????? ff742414 } // n = 7, score = 100 // c9 | leave // c3 | ret // 53 | push ebx // 56 | push esi // 57 | push edi // 68???????? | // ff742414 | push dword ptr [esp + 0x14] $sequence_5 = { 57 8d458c 50 6a25 e8???????? 8d4510 50 } // n = 7, score = 100 // 57 | push edi // 8d458c | lea eax, [ebp - 0x74] // 50 | push eax // 6a25 | push 0x25 // e8???????? | // 8d4510 | lea eax, [ebp + 0x10] // 50 | push eax $sequence_6 = { e8???????? c20800 6a2c b8???????? e8???????? 8b7508 ffb644ffffff } // n = 7, score = 100 // e8???????? | // c20800 | ret 8 // 6a2c | push 0x2c // b8???????? | // e8???????? | // 8b7508 | mov esi, dword ptr [ebp + 8] // ffb644ffffff | push dword ptr [esi - 0xbc] $sequence_7 = { c1e004 8b0430 83f802 0f8455010000 83f801 0f844c010000 8b4a04 } // n = 7, score = 100 // c1e004 | shl eax, 4 // 8b0430 | mov eax, dword ptr [eax + esi] // 83f802 | cmp eax, 2 // 0f8455010000 | je 0x15b // 83f801 | cmp eax, 1 // 0f844c010000 | je 0x152 // 8b4a04 | mov ecx, dword ptr [edx + 4] $sequence_8 = { 636966 7261 646f 206175 746f 6d 61 } // n = 7, score = 100 // 636966 | arpl word ptr [ecx + 0x66], bp // 7261 | jb 0x63 // 646f | outsd dx, dword ptr fs:[esi] // 206175 | and byte ptr [ecx + 0x75], ah // 746f | je 0x71 // 6d | insd dword ptr es:[edi], dx // 61 | popal $sequence_9 = { 8365d800 8b07 8d4dd8 51 68???????? 57 c645fc01 } // n = 7, score = 100 // 8365d800 | and dword ptr [ebp - 0x28], 0 // 8b07 | mov eax, dword ptr [edi] // 8d4dd8 | lea ecx, [ebp - 0x28] // 51 | push ecx // 68???????? | // 57 | push edi // c645fc01 | mov byte ptr [ebp - 4], 1 condition: 7 of them and filesize < 1392640 }
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