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rule win_biscuit_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.biscuit." 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.biscuit" 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 = { e9???????? a1???????? 898588feffff 83bd88feffff00 0f85bb010000 bf???????? } // n = 6, score = 100 // e9???????? | // a1???????? | // 898588feffff | mov dword ptr [ebp - 0x178], eax // 83bd88feffff00 | cmp dword ptr [ebp - 0x178], 0 // 0f85bb010000 | jne 0x1c1 // bf???????? | $sequence_1 = { 84c0 894b04 0f84e8feffff 8b542418 52 } // n = 5, score = 100 // 84c0 | test al, al // 894b04 | mov dword ptr [ebx + 4], ecx // 0f84e8feffff | je 0xfffffeee // 8b542418 | mov edx, dword ptr [esp + 0x18] // 52 | push edx $sequence_2 = { 8a54040c 40 f6d2 8854040b 3bc1 } // n = 5, score = 100 // 8a54040c | mov dl, byte ptr [esp + eax + 0xc] // 40 | inc eax // f6d2 | not dl // 8854040b | mov byte ptr [esp + eax + 0xb], dl // 3bc1 | cmp eax, ecx $sequence_3 = { eb04 8b7c2424 8b4604 53 53 53 } // n = 6, score = 100 // eb04 | jmp 6 // 8b7c2424 | mov edi, dword ptr [esp + 0x24] // 8b4604 | mov eax, dword ptr [esi + 4] // 53 | push ebx // 53 | push ebx // 53 | push ebx $sequence_4 = { e9???????? 8b4de4 bf???????? 33c0 8d9980000000 83c9ff f2ae } // n = 7, score = 100 // e9???????? | // 8b4de4 | mov ecx, dword ptr [ebp - 0x1c] // bf???????? | // 33c0 | xor eax, eax // 8d9980000000 | lea ebx, [ecx + 0x80] // 83c9ff | or ecx, 0xffffffff // f2ae | repne scasb al, byte ptr es:[edi] $sequence_5 = { f2ae f7d1 49 3bd1 731f 8b7de0 8a0c1a } // n = 7, score = 100 // f2ae | repne scasb al, byte ptr es:[edi] // f7d1 | not ecx // 49 | dec ecx // 3bd1 | cmp edx, ecx // 731f | jae 0x21 // 8b7de0 | mov edi, dword ptr [ebp - 0x20] // 8a0c1a | mov cl, byte ptr [edx + ebx] $sequence_6 = { 740e 68???????? 57 e8???????? 83c408 f60610 } // n = 6, score = 100 // 740e | je 0x10 // 68???????? | // 57 | push edi // e8???????? | // 83c408 | add esp, 8 // f60610 | test byte ptr [esi], 0x10 $sequence_7 = { 899538feffff 83bd38feffff00 7511 8b85ccfeffff 2b45e4 8985c0feffff } // n = 6, score = 100 // 899538feffff | mov dword ptr [ebp - 0x1c8], edx // 83bd38feffff00 | cmp dword ptr [ebp - 0x1c8], 0 // 7511 | jne 0x13 // 8b85ccfeffff | mov eax, dword ptr [ebp - 0x134] // 2b45e4 | sub eax, dword ptr [ebp - 0x1c] // 8985c0feffff | mov dword ptr [ebp - 0x140], eax $sequence_8 = { c1e902 f3a5 8bc8 83e103 f3a4 68c8000000 ff15???????? } // n = 7, score = 100 // c1e902 | shr ecx, 2 // f3a5 | rep movsd dword ptr es:[edi], dword ptr [esi] // 8bc8 | mov ecx, eax // 83e103 | and ecx, 3 // f3a4 | rep movsb byte ptr es:[edi], byte ptr [esi] // 68c8000000 | push 0xc8 // ff15???????? | $sequence_9 = { 8bcb e8???????? 84c0 7426 8b7b04 8bcd 8bd1 } // n = 7, score = 100 // 8bcb | mov ecx, ebx // e8???????? | // 84c0 | test al, al // 7426 | je 0x28 // 8b7b04 | mov edi, dword ptr [ebx + 4] // 8bcd | mov ecx, ebp // 8bd1 | mov edx, ecx condition: 7 of them and filesize < 180224 }
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