Actor(s): Kimsuky
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rule win_grease_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.grease." 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.grease" 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 = { 52 50 683f000f00 50 50 50 } // n = 6, score = 400 // 52 | push edx // 50 | push eax // 683f000f00 | push 0xf003f // 50 | push eax // 50 | push eax // 50 | push eax $sequence_1 = { 48897c2430 4533c0 c74424283f000f00 897c2420 ff15???????? 85c0 } // n = 6, score = 300 // 48897c2430 | inc ecx // 4533c0 | mov ecx, 4 // c74424283f000f00 | inc ebp // 897c2420 | xor eax, eax // ff15???????? | // 85c0 | test eax, eax $sequence_2 = { 4533c9 48897c2440 4889442438 48897c2430 } // n = 4, score = 300 // 4533c9 | inc ebp // 48897c2440 | xor ecx, ecx // 4889442438 | dec eax // 48897c2430 | mov dword ptr [esp + 0x40], edi $sequence_3 = { 48897c2440 488d442450 4889442438 48897c2430 } // n = 4, score = 300 // 48897c2440 | mov edx, ebx // 488d442450 | mov dword ptr [esp + 0x28], 4 // 4889442438 | dec eax // 48897c2430 | mov dword ptr [esp + 0x20], eax $sequence_4 = { 488b4c2460 ff15???????? b801000000 488b8c2480020000 4833cc } // n = 5, score = 300 // 488b4c2460 | test eax, eax // ff15???????? | // b801000000 | jne 0xed // 488b8c2480020000 | dec eax // 4833cc | mov edx, ebx $sequence_5 = { ff15???????? 85c0 0f85e7000000 488b4c2460 488d442458 } // n = 5, score = 300 // ff15???????? | // 85c0 | dec eax // 0f85e7000000 | mov ecx, dword ptr [esp + 0x50] // 488b4c2460 | dec eax // 488d442458 | lea eax, [esp + 0x58] $sequence_6 = { 48895c2440 48895c2458 895c2460 48895c2468 } // n = 4, score = 300 // 48895c2440 | mov dword ptr [esp + 0x28], 4 // 48895c2458 | dec eax // 895c2460 | mov dword ptr [esp + 0x20], eax // 48895c2468 | dec eax $sequence_7 = { 85c0 7534 488b4c2450 488d442458 41b904000000 4533c0 } // n = 6, score = 300 // 85c0 | dec eax // 7534 | mov dword ptr [esp + 0x38], eax // 488b4c2450 | dec eax // 488d442458 | mov dword ptr [esp + 0x30], edi // 41b904000000 | test eax, eax // 4533c0 | jne 0x36 $sequence_8 = { 488d442458 41b904000000 4533c0 488bd3 c744242804000000 4889442420 ff15???????? } // n = 7, score = 300 // 488d442458 | lea eax, [esp + 0x58] // 41b904000000 | dec eax // 4533c0 | mov dword ptr [esp + 0x30], edi // 488bd3 | inc ebp // c744242804000000 | xor eax, eax // 4889442420 | mov dword ptr [esp + 0x28], 0xf003f // ff15???????? | $sequence_9 = { 8b3d???????? 7502 ffd7 8d842430030000 50 8d8c2438050000 } // n = 6, score = 200 // 8b3d???????? | // 7502 | mov ecx, dword ptr [esp + 0x50] // ffd7 | dec eax // 8d842430030000 | lea eax, [esp + 0x58] // 50 | inc ecx // 8d8c2438050000 | mov ecx, 4 $sequence_10 = { e9???????? c644341472 e9???????? c644341469 e9???????? c644341462 e9???????? } // n = 7, score = 200 // e9???????? | // c644341472 | mov byte ptr [esp + esi + 0x14], 0x72 // e9???????? | // c644341469 | mov byte ptr [esp + esi + 0x14], 0x69 // e9???????? | // c644341462 | mov byte ptr [esp + esi + 0x14], 0x62 // e9???????? | $sequence_11 = { c68434380b00002b e9???????? c68434380b00003e e9???????? } // n = 4, score = 200 // c68434380b00002b | mov byte ptr [esp + esi + 0xb38], 0x2b // e9???????? | // c68434380b00003e | mov byte ptr [esp + esi + 0xb38], 0x3e // e9???????? | $sequence_12 = { c684342c08000068 e9???????? c684342c08000078 e9???????? c684342c08000063 e9???????? } // n = 6, score = 200 // c684342c08000068 | mov byte ptr [esp + esi + 0x82c], 0x68 // e9???????? | // c684342c08000078 | mov byte ptr [esp + esi + 0x82c], 0x78 // e9???????? | // c684342c08000063 | mov byte ptr [esp + esi + 0x82c], 0x63 // e9???????? | $sequence_13 = { c6440c0874 e9???????? c6440c0867 e9???????? c6440c0861 e9???????? } // n = 6, score = 200 // c6440c0874 | mov byte ptr [esp + ecx + 8], 0x74 // e9???????? | // c6440c0867 | mov byte ptr [esp + ecx + 8], 0x67 // e9???????? | // c6440c0861 | mov byte ptr [esp + ecx + 8], 0x61 // e9???????? | $sequence_14 = { 50 8b44242c 68???????? 50 ffd6 85c0 8b35???????? } // n = 7, score = 200 // 50 | dec eax // 8b44242c | mov edx, ebx // 68???????? | // 50 | mov dword ptr [esp + 0x28], 4 // ffd6 | jne 0x36 // 85c0 | dec eax // 8b35???????? | $sequence_15 = { 50 e8???????? 83c428 85c0 7409 } // n = 5, score = 200 // 50 | xor eax, eax // e8???????? | // 83c428 | mov dword ptr [esp + 0x28], 0xf003f // 85c0 | mov dword ptr [esp + 0x20], edi // 7409 | dec eax $sequence_16 = { 0f85bc000000 8b4c240c 8b35???????? 50 } // n = 4, score = 200 // 0f85bc000000 | mov ecx, 4 // 8b4c240c | inc ebp // 8b35???????? | // 50 | xor eax, eax $sequence_17 = { ffd6 85c0 7533 50 8d542410 52 } // n = 6, score = 200 // ffd6 | inc ebp // 85c0 | xor eax, eax // 7533 | inc ecx // 50 | mov ecx, 4 // 8d542410 | inc ebp // 52 | xor eax, eax $sequence_18 = { 6a04 50 53 52 ff15???????? 8b44240c 50 } // n = 7, score = 200 // 6a04 | dec eax // 50 | mov edx, ebx // 53 | mov dword ptr [esp + 0x28], 4 // 52 | dec eax // ff15???????? | // 8b44240c | mov dword ptr [esp + 0x20], eax // 50 | dec eax $sequence_19 = { b901000000 88843424060000 33c0 8a843424060000 } // n = 4, score = 200 // b901000000 | mov ecx, 1 // 88843424060000 | mov byte ptr [esp + esi + 0x624], al // 33c0 | xor eax, eax // 8a843424060000 | mov al, byte ptr [esp + esi + 0x624] $sequence_20 = { 8d442452 6a00 50 66a5 e8???????? } // n = 5, score = 200 // 8d442452 | mov ecx, dword ptr [esp + 0x50] // 6a00 | dec eax // 50 | lea eax, [esp + 0x58] // 66a5 | inc ecx // e8???????? | $sequence_21 = { c68434180300002e eb08 c68434180300002c 85c9 7408 80843418030000e0 46 } // n = 7, score = 200 // c68434180300002e | mov byte ptr [esp + esi + 0x318], 0x2e // eb08 | jmp 0xa // c68434180300002c | mov byte ptr [esp + esi + 0x318], 0x2c // 85c9 | test ecx, ecx // 7408 | je 0xa // 80843418030000e0 | add byte ptr [esp + esi + 0x318], 0xe0 // 46 | inc esi $sequence_22 = { eb1c c68434280700003f eb12 c68434280700002e eb08 } // n = 5, score = 200 // eb1c | jmp 0x1e // c68434280700003f | mov byte ptr [esp + esi + 0x728], 0x3f // eb12 | jmp 0x14 // c68434280700002e | mov byte ptr [esp + esi + 0x728], 0x2e // eb08 | jmp 0xa condition: 7 of them and filesize < 278528 }
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