Actor(s): BuhTrap
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rule win_buhtrap_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.buhtrap." 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.buhtrap" 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 = { e8???????? 59 59 84c0 0f8435010000 } // n = 5, score = 500 // e8???????? | // 59 | pop ecx // 59 | pop ecx // 84c0 | test al, al // 0f8435010000 | je 0x13b $sequence_1 = { e8???????? 8d95f4feffff 8bc8 e8???????? 8ad8 84db 0f8599000000 } // n = 7, score = 400 // e8???????? | // 8d95f4feffff | lea edx, [ebp - 0x10c] // 8bc8 | mov ecx, eax // e8???????? | // 8ad8 | mov bl, al // 84db | test bl, bl // 0f8599000000 | jne 0x9f $sequence_2 = { 89442438 85c9 7405 e8???????? 8b44240c } // n = 5, score = 400 // 89442438 | mov dword ptr [esp + 0x38], eax // 85c9 | test ecx, ecx // 7405 | je 7 // e8???????? | // 8b44240c | mov eax, dword ptr [esp + 0xc] $sequence_3 = { 57 6a0a ff35???????? ff15???????? } // n = 4, score = 400 // 57 | push edi // 6a0a | push 0xa // ff35???????? | // ff15???????? | $sequence_4 = { 8d54241c ff7510 83c602 8d8c2468010000 ff750c 89742424 } // n = 6, score = 400 // 8d54241c | lea edx, [esp + 0x1c] // ff7510 | push dword ptr [ebp + 0x10] // 83c602 | add esi, 2 // 8d8c2468010000 | lea ecx, [esp + 0x168] // ff750c | push dword ptr [ebp + 0xc] // 89742424 | mov dword ptr [esp + 0x24], esi $sequence_5 = { ff15???????? 8b45f4 6a3a 50 c6041800 ffd6 } // n = 6, score = 400 // ff15???????? | // 8b45f4 | mov eax, dword ptr [ebp - 0xc] // 6a3a | push 0x3a // 50 | push eax // c6041800 | mov byte ptr [eax + ebx], 0 // ffd6 | call esi $sequence_6 = { 8945e8 e8???????? 6a0d 5a b9???????? 8945ec } // n = 6, score = 400 // 8945e8 | mov dword ptr [ebp - 0x18], eax // e8???????? | // 6a0d | push 0xd // 5a | pop edx // b9???????? | // 8945ec | mov dword ptr [ebp - 0x14], eax $sequence_7 = { 56 ff75dc ffd7 6804010000 56 ff75d8 ffd3 } // n = 7, score = 400 // 56 | push esi // ff75dc | push dword ptr [ebp - 0x24] // ffd7 | call edi // 6804010000 | push 0x104 // 56 | push esi // ff75d8 | push dword ptr [ebp - 0x28] // ffd3 | call ebx $sequence_8 = { 75f5 3bf3 7560 6a14 e8???????? } // n = 5, score = 100 // 75f5 | jne 0xfffffff7 // 3bf3 | cmp esi, ebx // 7560 | jne 0x62 // 6a14 | push 0x14 // e8???????? | $sequence_9 = { 53 8d7dcc e8???????? 59 eb09 8bc3 e8???????? } // n = 7, score = 100 // 53 | push ebx // 8d7dcc | lea edi, [ebp - 0x34] // e8???????? | // 59 | pop ecx // eb09 | jmp 0xb // 8bc3 | mov eax, ebx // e8???????? | $sequence_10 = { 33ff 8975fc 3975f8 0f8611010000 33db 43 8d45d8 } // n = 7, score = 100 // 33ff | xor edi, edi // 8975fc | mov dword ptr [ebp - 4], esi // 3975f8 | cmp dword ptr [ebp - 8], esi // 0f8611010000 | jbe 0x117 // 33db | xor ebx, ebx // 43 | inc ebx // 8d45d8 | lea eax, [ebp - 0x28] $sequence_11 = { c645ff01 5f ff75f0 e8???????? ff75f8 } // n = 5, score = 100 // c645ff01 | mov byte ptr [ebp - 1], 1 // 5f | pop edi // ff75f0 | push dword ptr [ebp - 0x10] // e8???????? | // ff75f8 | push dword ptr [ebp - 8] $sequence_12 = { 83c302 85f6 75ec 5f 5e } // n = 5, score = 100 // 83c302 | add ebx, 2 // 85f6 | test esi, esi // 75ec | jne 0xffffffee // 5f | pop edi // 5e | pop esi $sequence_13 = { ff75f8 ffd7 85c0 7513 } // n = 4, score = 100 // ff75f8 | push dword ptr [ebp - 8] // ffd7 | call edi // 85c0 | test eax, eax // 7513 | jne 0x15 $sequence_14 = { 8d7df4 8d75f8 8bc3 e8???????? 33ff eb3e } // n = 6, score = 100 // 8d7df4 | lea edi, [ebp - 0xc] // 8d75f8 | lea esi, [ebp - 8] // 8bc3 | mov eax, ebx // e8???????? | // 33ff | xor edi, edi // eb3e | jmp 0x40 condition: 7 of them and filesize < 131072 }
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