Actor(s): Lazarus Group
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rule win_coredn_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2021-10-07" 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 = "20211007" malpedia_hash = "e5b790e0f888f252d49063a1251ca60ec2832535" malpedia_version = "20211008" 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, dword ptr [ebp - 4] // 8bf1 | mov esi, ecx // 50 | push eax // e8???????? | // 85c0 | test eax, eax $sequence_1 = { 0f1f440000 3811 7408 41 83e801 75f6 } // n = 6, score = 400 // 0f1f440000 | nop dword ptr [eax + eax] // 3811 | cmp byte ptr [ecx], dl // 7408 | je 0xa // 41 | inc ecx // 83e801 | sub eax, 1 // 75f6 | jne 0xfffffff8 $sequence_2 = { ff36 e8???????? 8b06 33d2 3810 7436 8b0e } // n = 7, score = 400 // ff36 | push dword ptr [esi] // e8???????? | // 8b06 | mov eax, dword ptr [esi] // 33d2 | xor edx, edx // 3810 | cmp byte ptr [eax], dl // 7436 | je 0x38 // 8b0e | mov ecx, dword ptr [esi] $sequence_3 = { 6a01 50 e8???????? 83c408 57 8b3e } // n = 6, score = 400 // 6a01 | push 1 // 50 | push eax // e8???????? | // 83c408 | add esp, 8 // 57 | push edi // 8b3e | mov edi, dword ptr [esi] $sequence_4 = { 8801 41 83ea01 75e7 8851ff b87a000780 5e } // n = 7, score = 400 // 8801 | mov byte ptr [ecx], al // 41 | inc ecx // 83ea01 | sub edx, 1 // 75e7 | jne 0xffffffe9 // 8851ff | mov byte ptr [ecx - 1], dl // b87a000780 | mov eax, 0x8007007a // 5e | pop esi $sequence_5 = { 75f9 2bca 7444 56 8bf3 } // n = 5, score = 400 // 75f9 | jne 0xfffffffb // 2bca | sub ecx, edx // 7444 | je 0x46 // 56 | push esi // 8bf3 | mov esi, ebx $sequence_6 = { 57 8bfb 83f904 7e70 8bd9 0fb607 83eb04 } // n = 7, score = 400 // 57 | push edi // 8bfb | mov edi, ebx // 83f904 | cmp ecx, 4 // 7e70 | jle 0x72 // 8bd9 | mov ebx, ecx // 0fb607 | movzx eax, byte ptr [edi] // 83eb04 | sub ebx, 4 $sequence_7 = { 7f97 891e 8b5df4 8b06 83f801 7e20 0fb64701 } // n = 7, score = 400 // 7f97 | jg 0xffffff99 // 891e | mov dword ptr [esi], ebx // 8b5df4 | mov ebx, dword ptr [ebp - 0xc] // 8b06 | mov eax, dword ptr [esi] // 83f801 | cmp eax, 1 // 7e20 | jle 0x22 // 0fb64701 | movzx eax, byte ptr [edi + 1] $sequence_8 = { 2bf9 90 8d0416 85c0 7420 8a040f } // n = 6, score = 400 // 2bf9 | sub edi, ecx // 90 | nop // 8d0416 | lea eax, dword ptr [esi + edx] // 85c0 | test eax, eax // 7420 | je 0x22 // 8a040f | mov al, byte ptr [edi + ecx] $sequence_9 = { 8b06 880a 42 83f803 7e1c } // n = 5, score = 400 // 8b06 | mov eax, dword ptr [esi] // 880a | mov byte ptr [edx], cl // 42 | inc edx // 83f803 | cmp eax, 3 // 7e1c | jle 0x1e $sequence_10 = { 8d85f0fcffff 6a00 50 e8???????? 6804010000 8d85f8feffff 6a00 } // n = 7, score = 400 // 8d85f0fcffff | lea eax, dword ptr [ebp - 0x310] // 6a00 | push 0 // 50 | push eax // e8???????? | // 6804010000 | push 0x104 // 8d85f8feffff | lea eax, dword ptr [ebp - 0x108] // 6a00 | push 0 $sequence_11 = { 56 8b7508 ba04010000 2bf1 6690 8d82fafeff7f } // n = 6, score = 400 // 56 | push esi // 8b7508 | mov esi, dword ptr [ebp + 8] // ba04010000 | mov edx, 0x104 // 2bf1 | sub esi, ecx // 6690 | nop // 8d82fafeff7f | lea eax, dword ptr [edx + 0x7ffffefa] $sequence_12 = { c60200 6a00 53 2bf8 e8???????? } // n = 5, score = 400 // c60200 | mov byte ptr [edx], 0 // 6a00 | push 0 // 53 | push ebx // 2bf8 | sub edi, eax // e8???????? | $sequence_13 = { 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_14 = { 0f8474010000 7823 66660f1f840000000000 8b0e 0fbe4419ff } // n = 5, score = 400 // 0f8474010000 | je 0x17a // 7823 | js 0x25 // 66660f1f840000000000 | nop word ptr [eax + eax] // 8b0e | mov ecx, dword ptr [esi] // 0fbe4419ff | movsx eax, byte ptr [ecx + ebx - 1] $sequence_15 = { e8???????? 83c41c 893e 5f 5e 5b 8be5 } // n = 7, score = 400 // e8???????? | // 83c41c | add esp, 0x1c // 893e | mov dword ptr [esi], edi // 5f | pop edi // 5e | pop esi // 5b | pop ebx // 8be5 | mov esp, ebp $sequence_16 = { c0e804 0ac8 880a 0fb64702 } // n = 4, score = 400 // c0e804 | shr al, 4 // 0ac8 | or cl, al // 880a | mov byte ptr [edx], cl // 0fb64702 | movzx eax, byte ptr [edi + 2] $sequence_17 = { 5e 5d c20400 85d2 750d 8851ff } // n = 6, score = 400 // 5e | pop esi // 5d | pop ebp // c20400 | ret 4 // 85d2 | test edx, edx // 750d | jne 0xf // 8851ff | mov byte ptr [ecx - 1], dl $sequence_18 = { 53 6a00 6a00 ff15???????? 8bd3 8bf8 } // n = 6, score = 400 // 53 | push ebx // 6a00 | push 0 // 6a00 | push 0 // ff15???????? | // 8bd3 | mov edx, ebx // 8bf8 | mov edi, eax $sequence_19 = { e8???????? 8b4e08 8d5701 83c40c } // n = 4, score = 400 // e8???????? | // 8b4e08 | mov ecx, dword ptr [esi + 8] // 8d5701 | lea edx, dword ptr [edi + 1] // 83c40c | add esp, 0xc $sequence_20 = { 48 bf7a000780 c60000 8bc7 5f 5b } // n = 6, score = 400 // 48 | dec eax // bf7a000780 | mov edi, 0x8007007a // c60000 | mov byte ptr [eax], 0 // 8bc7 | mov eax, edi // 5f | pop edi // 5b | pop ebx $sequence_21 = { 8bf2 8bd9 895df4 8b06 8945ec } // n = 5, score = 400 // 8bf2 | mov esi, edx // 8bd9 | mov ebx, ecx // 895df4 | mov dword ptr [ebp - 0xc], ebx // 8b06 | mov eax, dword ptr [esi] // 8945ec | mov dword ptr [ebp - 0x14], eax $sequence_22 = { 83c404 8907 85c0 741a 8d4e20 } // n = 5, score = 400 // 83c404 | add esp, 4 // 8907 | mov dword ptr [edi], eax // 85c0 | test eax, eax // 741a | je 0x1c // 8d4e20 | lea ecx, dword ptr [esi + 0x20] condition: 7 of them and filesize < 385024 }
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