Actor(s): Lazarus Group
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rule win_badcall_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" version = "1" description = "Detects win.badcall." 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.badcall" malpedia_rule_date = "20220513" malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26" malpedia_version = "20220516" 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 = { c20800 53 8b5c2410 57 53 } // n = 5, score = 300 // c20800 | ret 8 // 53 | push ebx // 8b5c2410 | mov ebx, dword ptr [esp + 0x10] // 57 | push edi // 53 | push ebx $sequence_1 = { 83c40c 85c0 7e06 03f0 3bf7 7ce1 } // n = 6, score = 300 // 83c40c | add esp, 0xc // 85c0 | test eax, eax // 7e06 | jle 8 // 03f0 | add esi, eax // 3bf7 | cmp esi, edi // 7ce1 | jl 0xffffffe3 $sequence_2 = { 51 8bce e8???????? 85c0 7407 5f } // n = 6, score = 300 // 51 | push ecx // 8bce | mov ecx, esi // e8???????? | // 85c0 | test eax, eax // 7407 | je 9 // 5f | pop edi $sequence_3 = { 68???????? a3???????? a3???????? a3???????? a1???????? 50 c705????????04000000 } // n = 7, score = 300 // 68???????? | // a3???????? | // a3???????? | // a3???????? | // a1???????? | // 50 | push eax // c705????????04000000 | $sequence_4 = { 52 c744241800000000 ffd3 5e 5d } // n = 5, score = 300 // 52 | push edx // c744241800000000 | mov dword ptr [esp + 0x18], 0 // ffd3 | call ebx // 5e | pop esi // 5d | pop ebp $sequence_5 = { 8b442404 48 7455 48 } // n = 4, score = 300 // 8b442404 | mov eax, dword ptr [esp + 4] // 48 | dec eax // 7455 | je 0x57 // 48 | dec eax $sequence_6 = { 68ffff0000 50 66c74424180100 66c744241a0000 ff15???????? } // n = 5, score = 300 // 68ffff0000 | push 0xffff // 50 | push eax // 66c74424180100 | mov word ptr [esp + 0x18], 1 // 66c744241a0000 | mov word ptr [esp + 0x1a], 0 // ff15???????? | $sequence_7 = { ff15???????? c20400 c705????????01000000 a1???????? 68???????? } // n = 5, score = 300 // ff15???????? | // c20400 | ret 4 // c705????????01000000 | // a1???????? | // 68???????? | $sequence_8 = { 89542412 6689542416 ff15???????? 8b4e04 6689442406 8d442404 } // n = 6, score = 300 // 89542412 | mov dword ptr [esp + 0x12], edx // 6689542416 | mov word ptr [esp + 0x16], dx // ff15???????? | // 8b4e04 | mov ecx, dword ptr [esi + 4] // 6689442406 | mov word ptr [esp + 6], ax // 8d442404 | lea eax, [esp + 4] $sequence_9 = { 50 c705????????04000000 ff15???????? c20400 a1???????? 68???????? } // n = 6, score = 300 // 50 | push eax // c705????????04000000 | // ff15???????? | // c20400 | ret 4 // a1???????? | // 68???????? | $sequence_10 = { 83e803 7557 33c0 68???????? a3???????? a3???????? } // n = 6, score = 300 // 83e803 | sub eax, 3 // 7557 | jne 0x59 // 33c0 | xor eax, eax // 68???????? | // a3???????? | // a3???????? | $sequence_11 = { 7455 48 7434 83e803 } // n = 4, score = 300 // 7455 | je 0x57 // 48 | dec eax // 7434 | je 0x36 // 83e803 | sub eax, 3 $sequence_12 = { e8???????? 8b4604 8bcf 50 e8???????? 5f b801000000 } // n = 7, score = 300 // e8???????? | // 8b4604 | mov eax, dword ptr [esi + 4] // 8bcf | mov ecx, edi // 50 | push eax // e8???????? | // 5f | pop edi // b801000000 | mov eax, 1 $sequence_13 = { 8d7c2411 895c2408 f3ab 66ab aa } // n = 5, score = 300 // 8d7c2411 | lea edi, [esp + 0x11] // 895c2408 | mov dword ptr [esp + 8], ebx // f3ab | rep stosd dword ptr es:[edi], eax // 66ab | stosw word ptr es:[edi], ax // aa | stosb byte ptr es:[edi], al $sequence_14 = { 2bfd 83c408 d1ff 66c7847c3e0100000000 } // n = 4, score = 200 // 2bfd | sub edi, ebp // 83c408 | add esp, 8 // d1ff | sar edi, 1 // 66c7847c3e0100000000 | mov word ptr [esp + edi*2 + 0x13e], 0 $sequence_15 = { 83c408 53 e8???????? 83c404 85c0 7426 53 } // n = 7, score = 200 // 83c408 | add esp, 8 // 53 | push ebx // e8???????? | // 83c404 | add esp, 4 // 85c0 | test eax, eax // 7426 | je 0x28 // 53 | push ebx condition: 7 of them and filesize < 483328 }
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