Actor(s): Lazarus Group
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rule win_bravonc_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.bravonc." 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.bravonc" malpedia_rule_date = "20260105" malpedia_hash = "19b79e7cab4eaf532122e5b45a77dd8f6bb5cc79" malpedia_version = "20251219" 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 = { 8b4838 334820 334818 33480c } // n = 4, score = 100 // 8b4838 | mov ecx, dword ptr [eax + 0x38] // 334820 | xor ecx, dword ptr [eax + 0x20] // 334818 | xor ecx, dword ptr [eax + 0x18] // 33480c | xor ecx, dword ptr [eax + 0xc] $sequence_1 = { 68???????? e8???????? e8???????? be???????? 68???????? 56 c705????????03000000 } // n = 7, score = 100 // 68???????? | // e8???????? | // e8???????? | // be???????? | // 68???????? | // 56 | push esi // c705????????03000000 | $sequence_2 = { 8bce e8???????? eb03 8b7d08 8b1d???????? 8d45f4 } // n = 6, score = 100 // 8bce | mov ecx, esi // e8???????? | // eb03 | jmp 5 // 8b7d08 | mov edi, dword ptr [ebp + 8] // 8b1d???????? | // 8d45f4 | lea eax, [ebp - 0xc] $sequence_3 = { 33480c 334804 51 e8???????? 8b8ec0000000 53 ff75f0 } // n = 7, score = 100 // 33480c | xor ecx, dword ptr [eax + 0xc] // 334804 | xor ecx, dword ptr [eax + 4] // 51 | push ecx // e8???????? | // 8b8ec0000000 | mov ecx, dword ptr [esi + 0xc0] // 53 | push ebx // ff75f0 | push dword ptr [ebp - 0x10] $sequence_4 = { 334dec 57 ff75fc 334dfc } // n = 4, score = 100 // 334dec | xor ecx, dword ptr [ebp - 0x14] // 57 | push edi // ff75fc | push dword ptr [ebp - 4] // 334dfc | xor ecx, dword ptr [ebp - 4] $sequence_5 = { 5e c9 c20c00 55 8bec 81ec80020000 53 } // n = 7, score = 100 // 5e | pop esi // c9 | leave // c20c00 | ret 0xc // 55 | push ebp // 8bec | mov ebp, esp // 81ec80020000 | sub esp, 0x280 // 53 | push ebx $sequence_6 = { 57 8bce ff15???????? 8bc6 5f 5e c9 } // n = 7, score = 100 // 57 | push edi // 8bce | mov ecx, esi // ff15???????? | // 8bc6 | mov eax, esi // 5f | pop edi // 5e | pop esi // c9 | leave $sequence_7 = { 8945f4 8b06 f7d8 23c1 03f3 8945fc } // n = 6, score = 100 // 8945f4 | mov dword ptr [ebp - 0xc], eax // 8b06 | mov eax, dword ptr [esi] // f7d8 | neg eax // 23c1 | and eax, ecx // 03f3 | add esi, ebx // 8945fc | mov dword ptr [ebp - 4], eax $sequence_8 = { 334834 6a01 334828 334814 51 } // n = 5, score = 100 // 334834 | xor ecx, dword ptr [eax + 0x34] // 6a01 | push 1 // 334828 | xor ecx, dword ptr [eax + 0x28] // 334814 | xor ecx, dword ptr [eax + 0x14] // 51 | push ecx $sequence_9 = { eb02 33db 6a01 e8???????? 84c0 59 750d } // n = 7, score = 100 // eb02 | jmp 4 // 33db | xor ebx, ebx // 6a01 | push 1 // e8???????? | // 84c0 | test al, al // 59 | pop ecx // 750d | jne 0xf condition: 7 of them and filesize < 131072 }
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