Actor(s): Lazarus Group
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rule win_coredn_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.coredn." 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.coredn" 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 = { 51 56 8d45fc 8bf1 50 e8???????? 85c0 } // n = 7, score = 600 // 51 | push ecx // 56 | push esi // 8d45fc | lea eax, [ebp - 4] // 8bf1 | mov esi, ecx // 50 | push eax // e8???????? | // 85c0 | test eax, eax $sequence_1 = { 6690 8d82fafeff7f 85c0 741c 8a040e } // n = 5, score = 400 // 6690 | nop // 8d82fafeff7f | lea eax, [edx + 0x7ffffefa] // 85c0 | test eax, eax // 741c | je 0x1e // 8a040e | mov al, byte ptr [esi + ecx] $sequence_2 = { 84c0 7415 8801 41 83ea01 } // n = 5, score = 400 // 84c0 | test al, al // 7415 | je 0x17 // 8801 | mov byte ptr [ecx], al // 41 | inc ecx // 83ea01 | sub edx, 1 $sequence_3 = { 2bf9 90 8d0416 85c0 } // n = 4, score = 400 // 2bf9 | sub edi, ecx // 90 | nop // 8d0416 | lea eax, [esi + edx] // 85c0 | test eax, eax $sequence_4 = { 8bec 56 8b7508 ba04010000 2bf1 6690 8d82fafeff7f } // n = 7, score = 400 // 8bec | mov ebp, esp // 56 | push esi // 8b7508 | mov esi, dword ptr [ebp + 8] // ba04010000 | mov edx, 0x104 // 2bf1 | sub esi, ecx // 6690 | nop // 8d82fafeff7f | lea eax, [edx + 0x7ffffefa] $sequence_5 = { 741c 8818 4a 40 83e901 75ec } // n = 6, score = 400 // 741c | je 0x1e // 8818 | mov byte ptr [eax], bl // 4a | dec edx // 40 | inc eax // 83e901 | sub ecx, 1 // 75ec | jne 0xffffffee $sequence_6 = { 7408 81faffffff7f 7605 b857000780 85c0 784f } // n = 6, score = 400 // 7408 | je 0xa // 81faffffff7f | cmp edx, 0x7fffffff // 7605 | jbe 7 // b857000780 | mov eax, 0x80070057 // 85c0 | test eax, eax // 784f | js 0x51 $sequence_7 = { ff15???????? 8bd3 8bf8 8d4201 8a0a 42 } // n = 6, score = 400 // ff15???????? | // 8bd3 | mov edx, ebx // 8bf8 | mov edi, eax // 8d4201 | lea eax, [edx + 1] // 8a0a | mov cl, byte ptr [edx] // 42 | inc edx $sequence_8 = { 75ca 8b4608 5b 5f } // n = 4, score = 400 // 75ca | jne 0xffffffcc // 8b4608 | mov eax, dword ptr [esi + 8] // 5b | pop ebx // 5f | pop edi $sequence_9 = { 5d c20400 85d2 750d 8851ff b87a000780 5e } // n = 7, score = 400 // 5d | pop ebp // c20400 | ret 4 // 85d2 | test edx, edx // 750d | jne 0xf // 8851ff | mov byte ptr [ecx - 1], dl // b87a000780 | mov eax, 0x8007007a // 5e | pop esi $sequence_10 = { 53 8d5f20 53 e8???????? } // n = 4, score = 400 // 53 | push ebx // 8d5f20 | lea ebx, [edi + 0x20] // 53 | push ebx // e8???????? | $sequence_11 = { 740b 6a01 50 e8???????? 83c408 8b4608 } // n = 6, score = 400 // 740b | je 0xd // 6a01 | push 1 // 50 | push eax // e8???????? | // 83c408 | add esp, 8 // 8b4608 | mov eax, dword ptr [esi + 8] $sequence_12 = { b87a000780 5e 5d c20400 } // n = 4, score = 400 // b87a000780 | mov eax, 0x8007007a // 5e | pop esi // 5d | pop ebp // c20400 | ret 4 $sequence_13 = { 7423 8a1c06 84db 741c 8818 } // n = 5, score = 400 // 7423 | je 0x25 // 8a1c06 | mov bl, byte ptr [esi + eax] // 84db | test bl, bl // 741c | je 0x1e // 8818 | mov byte ptr [eax], bl $sequence_14 = { 8bc3 8811 5b 5d } // n = 4, score = 400 // 8bc3 | mov eax, ebx // 8811 | mov byte ptr [ecx], dl // 5b | pop ebx // 5d | pop ebp $sequence_15 = { 6a02 50 e8???????? 83c408 53 8bce } // n = 6, score = 400 // 6a02 | push 2 // 50 | push eax // e8???????? | // 83c408 | add esp, 8 // 53 | push ebx // 8bce | mov ecx, esi condition: 7 of them and filesize < 385024 }
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