Actor(s): BuhTrap
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rule win_buhtrap_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" 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 = "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 = { 59 59 84c0 0f8435010000 } // n = 4, score = 500 // 59 | pop ecx // 59 | pop ecx // 84c0 | test al, al // 0f8435010000 | je 0x13b $sequence_1 = { 7423 8b44240c 33d2 6a64 59 f7f1 } // n = 6, score = 400 // 7423 | je 0x25 // 8b44240c | mov eax, dword ptr [esp + 0xc] // 33d2 | xor edx, edx // 6a64 | push 0x64 // 59 | pop ecx // f7f1 | div ecx $sequence_2 = { c3 b301 ebe1 55 8bec 83ec18 } // n = 6, score = 400 // c3 | ret // b301 | mov bl, 1 // ebe1 | jmp 0xffffffe3 // 55 | push ebp // 8bec | mov ebp, esp // 83ec18 | sub esp, 0x18 $sequence_3 = { 6a00 50 8d442414 c744242c04000000 } // n = 4, score = 400 // 6a00 | push 0 // 50 | push eax // 8d442414 | lea eax, [esp + 0x14] // c744242c04000000 | mov dword ptr [esp + 0x2c], 4 $sequence_4 = { 6a06 8bce e8???????? 8a1d???????? 56 } // n = 5, score = 400 // 6a06 | push 6 // 8bce | mov ecx, esi // e8???????? | // 8a1d???????? | // 56 | push esi $sequence_5 = { 0f8489000000 837d1400 747b 6a09 59 33c0 8d7c242c } // n = 7, score = 400 // 0f8489000000 | je 0x8f // 837d1400 | cmp dword ptr [ebp + 0x14], 0 // 747b | je 0x7d // 6a09 | push 9 // 59 | pop ecx // 33c0 | xor eax, eax // 8d7c242c | lea edi, [esp + 0x2c] $sequence_6 = { 7405 e8???????? 85f6 7907 32c0 e9???????? 8365f000 } // n = 7, score = 400 // 7405 | je 7 // e8???????? | // 85f6 | test esi, esi // 7907 | jns 9 // 32c0 | xor al, al // e9???????? | // 8365f000 | and dword ptr [ebp - 0x10], 0 $sequence_7 = { ffd6 57 ffd6 33c0 85db 0f94c0 5f } // n = 7, score = 400 // ffd6 | call esi // 57 | push edi // ffd6 | call esi // 33c0 | xor eax, eax // 85db | test ebx, ebx // 0f94c0 | sete al // 5f | pop edi $sequence_8 = { 754e 6a01 53 50 } // n = 4, score = 100 // 754e | jne 0x50 // 6a01 | push 1 // 53 | push ebx // 50 | push eax $sequence_9 = { 53 68???????? 890e 894604 e8???????? 50 } // n = 6, score = 100 // 53 | push ebx // 68???????? | // 890e | mov dword ptr [esi], ecx // 894604 | mov dword ptr [esi + 4], eax // e8???????? | // 50 | push eax $sequence_10 = { 897dfc e8???????? 59 84c0 0f8497000000 3bdf } // n = 6, score = 100 // 897dfc | mov dword ptr [ebp - 4], edi // e8???????? | // 59 | pop ecx // 84c0 | test al, al // 0f8497000000 | je 0x9d // 3bdf | cmp ebx, edi $sequence_11 = { 6aff ff742420 ff7624 ffd7 ff742418 e8???????? } // n = 6, score = 100 // 6aff | push -1 // ff742420 | push dword ptr [esp + 0x20] // ff7624 | push dword ptr [esi + 0x24] // ffd7 | call edi // ff742418 | push dword ptr [esp + 0x18] // e8???????? | $sequence_12 = { ffd7 6a00 689385e784 6a28 68???????? } // n = 5, score = 100 // ffd7 | call edi // 6a00 | push 0 // 689385e784 | push 0x84e78593 // 6a28 | push 0x28 // 68???????? | $sequence_13 = { 894624 8b442414 894604 a808 7466 } // n = 5, score = 100 // 894624 | mov dword ptr [esi + 0x24], eax // 8b442414 | mov eax, dword ptr [esp + 0x14] // 894604 | mov dword ptr [esi + 4], eax // a808 | test al, 8 // 7466 | je 0x68 $sequence_14 = { 753d 8b4e2c 83c104 e8???????? e8???????? } // n = 5, score = 100 // 753d | jne 0x3f // 8b4e2c | mov ecx, dword ptr [esi + 0x2c] // 83c104 | add ecx, 4 // e8???????? | // e8???????? | condition: 7 of them and filesize < 131072 }
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