Actor(s): Kimsuky
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rule win_yorekey_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.yorekey." 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.yorekey" malpedia_rule_date = "20231130" malpedia_hash = "fc8a0e9f343f6d6ded9e7df1a64dac0cc68d7351" malpedia_version = "20230808" 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 = { 750a 85c0 7506 ff15???????? } // n = 4, score = 200 // 750a | jne 0xc // 85c0 | test eax, eax // 7506 | jne 8 // ff15???????? | $sequence_1 = { 4883ec20 33ff 488d1dc9fa0000 488b0b ff15???????? } // n = 5, score = 100 // 4883ec20 | lea ecx, [edi + 4] // 33ff | dec eax // 488d1dc9fa0000 | mov dword ptr [esp + 0x28], eax // 488b0b | dec esp // ff15???????? | $sequence_2 = { 33c9 ff15???????? 488bd8 ff15???????? 3db7000000 7509 } // n = 6, score = 100 // 33c9 | test eax, eax // ff15???????? | // 488bd8 | jae 0xf // ff15???????? | // 3db7000000 | dec eax // 7509 | mov edx, ebx $sequence_3 = { 8bc6 83f801 7521 a1???????? 50 ff15???????? 68???????? } // n = 7, score = 100 // 8bc6 | test edi, edi // 83f801 | dec eax // 7521 | sub esp, 0x20 // a1???????? | // 50 | xor edi, edi // ff15???????? | // 68???????? | $sequence_4 = { 03048de0404100 eb02 8bc2 f6402480 0f8571ffffff 33f6 3bfe } // n = 7, score = 100 // 03048de0404100 | lea ecx, [esp + 0x30] // eb02 | dec eax // 8bc2 | lea edx, [esp + 0x38] // f6402480 | inc esp // 0f8571ffffff | mov eax, ebx // 33f6 | dec eax // 3bfe | mov dword ptr [esp + 0x20], 0 $sequence_5 = { 4803d1 488d0d02090100 442bc6 488b0cc1 498b0c0c ff15???????? 85c0 } // n = 7, score = 100 // 4803d1 | dec eax // 488d0d02090100 | add edx, ecx // 442bc6 | dec eax // 488b0cc1 | lea ecx, [0x10902] // 498b0c0c | inc esp // ff15???????? | // 85c0 | sub eax, esi $sequence_6 = { 7530 a1???????? ba???????? 50 e9???????? a1???????? } // n = 6, score = 100 // 7530 | dec eax // a1???????? | // ba???????? | // 50 | lea ebx, [0xfac9] // e9???????? | // a1???????? | $sequence_7 = { 488bce e8???????? 488d154c040100 4c63c8 418d4902 } // n = 5, score = 100 // 488bce | lea eax, [0xfffffacb] // e8???????? | // 488d154c040100 | je 7 // 4c63c8 | inc cx // 418d4902 | mov dword ptr [ebp], ecx $sequence_8 = { 730d 488bd3 488bcf e8???????? eb1c } // n = 5, score = 100 // 730d | dec eax // 488bd3 | mov ecx, dword ptr [ecx + eax*8] // 488bcf | dec ecx // e8???????? | // eb1c | mov ecx, dword ptr [esp + ecx] $sequence_9 = { 751b 6a02 33c9 51 } // n = 4, score = 100 // 751b | mov dword ptr [ebp - 0x90], eax // 6a02 | mov dword ptr [ebp - 0x94], eax // 33c9 | lea eax, [ebp - 0x68] // 51 | mov ecx, 0x19 $sequence_10 = { 7405 6641894d00 4885f6 7457 483bf7 7252 4d85ff } // n = 7, score = 100 // 7405 | dec eax // 6641894d00 | mov ebx, eax // 4885f6 | cmp eax, 0xb7 // 7457 | jne 0xb // 483bf7 | dec eax // 7252 | lea eax, [esp + 0x3c] // 4d85ff | inc esp $sequence_11 = { 898570ffffff 89856cffffff 8d4598 b919000000 } // n = 4, score = 100 // 898570ffffff | dec eax // 89856cffffff | mov ecx, dword ptr [ebx] // 8d4598 | dec eax // b919000000 | mov ecx, esi $sequence_12 = { ff15???????? 488d44243c 448d4f04 4889442428 4c8d05cbfaffff } // n = 5, score = 100 // ff15???????? | // 488d44243c | dec eax // 448d4f04 | mov ecx, edi // 4889442428 | jmp 0x26 // 4c8d05cbfaffff | xor ecx, ecx $sequence_13 = { 5a 8985c4fbffff 3bc2 0f8451ffffff 83f807 0f87110a0000 ff2485b19b4000 } // n = 7, score = 100 // 5a | jne 0xc // 8985c4fbffff | test eax, eax // 3bc2 | jne 0xa // 0f8451ffffff | mov eax, esi // 83f807 | cmp eax, 1 // 0f87110a0000 | jne 0x26 // ff2485b19b4000 | push eax $sequence_14 = { 55 8bec 51 8bc2 56 8d7002 8d9b00000000 } // n = 7, score = 100 // 55 | dec eax // 8bec | lea edx, [0x1044c] // 51 | dec esp // 8bc2 | arpl ax, cx // 56 | inc ecx // 8d7002 | lea ecx, [ecx + 2] // 8d9b00000000 | dec esp condition: 7 of them and filesize < 274432 }
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