Actor(s): Lazarus Group, Silent Chollima
There is no description at this point.
rule win_bistromath_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.bistromath." 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.bistromath" malpedia_rule_date = "20230705" malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41" malpedia_version = "20230715" 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 = { c744242c00000000 eb0b 8bce e8???????? 8944242c 8b44240c 33f6 } // n = 7, score = 400 // c744242c00000000 | mov dword ptr [esp + 0x2c], 0 // eb0b | jmp 0xd // 8bce | mov ecx, esi // e8???????? | // 8944242c | mov dword ptr [esp + 0x2c], eax // 8b44240c | mov eax, dword ptr [esp + 0xc] // 33f6 | xor esi, esi $sequence_1 = { 8bcb 23550c 234d10 0bd1 750f 0bf3 7506 } // n = 7, score = 400 // 8bcb | mov ecx, ebx // 23550c | and edx, dword ptr [ebp + 0xc] // 234d10 | and ecx, dword ptr [ebp + 0x10] // 0bd1 | or edx, ecx // 750f | jne 0x11 // 0bf3 | or esi, ebx // 7506 | jne 8 $sequence_2 = { c704b0???????? 8b4748 8b75d8 894108 ff4748 8b4108 8945c0 } // n = 7, score = 400 // c704b0???????? | // 8b4748 | mov eax, dword ptr [edi + 0x48] // 8b75d8 | mov esi, dword ptr [ebp - 0x28] // 894108 | mov dword ptr [ecx + 8], eax // ff4748 | inc dword ptr [edi + 0x48] // 8b4108 | mov eax, dword ptr [ecx + 8] // 8945c0 | mov dword ptr [ebp - 0x40], eax $sequence_3 = { ff461c 8b55f8 89548804 8b55d4 66c704885d00 c644880300 89548808 } // n = 7, score = 400 // ff461c | inc dword ptr [esi + 0x1c] // 8b55f8 | mov edx, dword ptr [ebp - 8] // 89548804 | mov dword ptr [eax + ecx*4 + 4], edx // 8b55d4 | mov edx, dword ptr [ebp - 0x2c] // 66c704885d00 | mov word ptr [eax + ecx*4], 0x5d // c644880300 | mov byte ptr [eax + ecx*4 + 3], 0 // 89548808 | mov dword ptr [eax + ecx*4 + 8], edx $sequence_4 = { 8bce e8???????? 837c242800 0f85e2000000 8b442418 8b480c f6412c20 } // n = 7, score = 400 // 8bce | mov ecx, esi // e8???????? | // 837c242800 | cmp dword ptr [esp + 0x28], 0 // 0f85e2000000 | jne 0xe8 // 8b442418 | mov eax, dword ptr [esp + 0x18] // 8b480c | mov ecx, dword ptr [eax + 0xc] // f6412c20 | test byte ptr [ecx + 0x2c], 0x20 $sequence_5 = { e8???????? 8b4df0 83c408 85c9 7421 8b7108 83ff01 } // n = 7, score = 400 // e8???????? | // 8b4df0 | mov ecx, dword ptr [ebp - 0x10] // 83c408 | add esp, 8 // 85c9 | test ecx, ecx // 7421 | je 0x23 // 8b7108 | mov esi, dword ptr [ecx + 8] // 83ff01 | cmp edi, 1 $sequence_6 = { 8b8a00020000 0101 eb3e 3b9a0c010000 721e 3b9a10010000 7316 } // n = 7, score = 400 // 8b8a00020000 | mov ecx, dword ptr [edx + 0x200] // 0101 | add dword ptr [ecx], eax // eb3e | jmp 0x40 // 3b9a0c010000 | cmp ebx, dword ptr [edx + 0x10c] // 721e | jb 0x20 // 3b9a10010000 | cmp ebx, dword ptr [edx + 0x110] // 7316 | jae 0x18 $sequence_7 = { 8d04dd04000000 894df8 8b4df4 50 e8???????? 83c404 8945fc } // n = 7, score = 400 // 8d04dd04000000 | lea eax, [ebx*8 + 4] // 894df8 | mov dword ptr [ebp - 8], ecx // 8b4df4 | mov ecx, dword ptr [ebp - 0xc] // 50 | push eax // e8???????? | // 83c404 | add esp, 4 // 8945fc | mov dword ptr [ebp - 4], eax $sequence_8 = { 730a 0fb6c0 8954811c fe4113 c681b800000000 c781c000000000000000 8b91d8000000 } // n = 7, score = 400 // 730a | jae 0xc // 0fb6c0 | movzx eax, al // 8954811c | mov dword ptr [ecx + eax*4 + 0x1c], edx // fe4113 | inc byte ptr [ecx + 0x13] // c681b800000000 | mov byte ptr [ecx + 0xb8], 0 // c781c000000000000000 | mov dword ptr [ecx + 0xc0], 0 // 8b91d8000000 | mov edx, dword ptr [ecx + 0xd8] $sequence_9 = { e8???????? 8b45f8 c7473400000000 894738 5f 5e 5b } // n = 7, score = 400 // e8???????? | // 8b45f8 | mov eax, dword ptr [ebp - 8] // c7473400000000 | mov dword ptr [edi + 0x34], 0 // 894738 | mov dword ptr [edi + 0x38], eax // 5f | pop edi // 5e | pop esi // 5b | pop ebx condition: 7 of them and filesize < 33816576 }
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