Actor(s): DarkHotel
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rule win_ramsay_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-03-28" version = "1" description = "Detects win.ramsay." 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.ramsay" malpedia_rule_date = "20230328" malpedia_hash = "9d2d75cef573c1c2d861f5197df8f563b05a305d" malpedia_version = "20230407" 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 = { 83f820 7502 eb07 33c0 e9???????? } // n = 5, score = 600 // 83f820 | cmp eax, 0x20 // 7502 | jne 4 // eb07 | jmp 9 // 33c0 | xor eax, eax // e9???????? | $sequence_1 = { 85c0 7514 ff15???????? 83f820 7502 } // n = 5, score = 600 // 85c0 | test eax, eax // 7514 | jne 0x16 // ff15???????? | // 83f820 | cmp eax, 0x20 // 7502 | jne 4 $sequence_2 = { ff15???????? 85c0 7502 eb02 ebb1 } // n = 5, score = 600 // ff15???????? | // 85c0 | test eax, eax // 7502 | jne 4 // eb02 | jmp 4 // ebb1 | jmp 0xffffffb3 $sequence_3 = { 8d45f0 50 8b4dfc 51 e8???????? 83f86f } // n = 6, score = 500 // 8d45f0 | lea eax, [ebp - 0x10] // 50 | push eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 51 | push ecx // e8???????? | // 83f86f | cmp eax, 0x6f $sequence_4 = { c745f088020000 c745f400000000 6888020000 e8???????? 83c404 8945fc } // n = 6, score = 500 // c745f088020000 | mov dword ptr [ebp - 0x10], 0x288 // c745f400000000 | mov dword ptr [ebp - 0xc], 0 // 6888020000 | push 0x288 // e8???????? | // 83c404 | add esp, 4 // 8945fc | mov dword ptr [ebp - 4], eax $sequence_5 = { 8b4d08 034df8 8b55e8 0355f8 8a8294010000 8801 ebd3 } // n = 7, score = 500 // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 034df8 | add ecx, dword ptr [ebp - 8] // 8b55e8 | mov edx, dword ptr [ebp - 0x18] // 0355f8 | add edx, dword ptr [ebp - 8] // 8a8294010000 | mov al, byte ptr [edx + 0x194] // 8801 | mov byte ptr [ecx], al // ebd3 | jmp 0xffffffd5 $sequence_6 = { 83bdc4fdffffff 7507 33c0 e9???????? } // n = 4, score = 500 // 83bdc4fdffffff | cmp dword ptr [ebp - 0x23c], -1 // 7507 | jne 9 // 33c0 | xor eax, eax // e9???????? | $sequence_7 = { 8b5508 8b4508 8a480b 884a1e 8b5508 8b4508 8a481c } // n = 7, score = 500 // 8b5508 | mov edx, dword ptr [ebp + 8] // 8b4508 | mov eax, dword ptr [ebp + 8] // 8a480b | mov cl, byte ptr [eax + 0xb] // 884a1e | mov byte ptr [edx + 0x1e], cl // 8b5508 | mov edx, dword ptr [ebp + 8] // 8b4508 | mov eax, dword ptr [ebp + 8] // 8a481c | mov cl, byte ptr [eax + 0x1c] $sequence_8 = { 8b4de8 8b11 8955e8 eba5 } // n = 4, score = 500 // 8b4de8 | mov ecx, dword ptr [ebp - 0x18] // 8b11 | mov edx, dword ptr [ecx] // 8955e8 | mov dword ptr [ebp - 0x18], edx // eba5 | jmp 0xffffffa7 $sequence_9 = { 8b5508 8b4508 8a4815 884a1e } // n = 4, score = 500 // 8b5508 | mov edx, dword ptr [ebp + 8] // 8b4508 | mov eax, dword ptr [ebp + 8] // 8a4815 | mov cl, byte ptr [eax + 0x15] // 884a1e | mov byte ptr [edx + 0x1e], cl $sequence_10 = { d1e2 52 6a00 8b45fc } // n = 4, score = 500 // d1e2 | shl edx, 1 // 52 | push edx // 6a00 | push 0 // 8b45fc | mov eax, dword ptr [ebp - 4] $sequence_11 = { ff15???????? 33c0 e9???????? e8???????? 85c0 7507 33c0 } // n = 7, score = 400 // ff15???????? | // 33c0 | xor eax, eax // e9???????? | // e8???????? | // 85c0 | test eax, eax // 7507 | jne 9 // 33c0 | xor eax, eax $sequence_12 = { e8???????? e8???????? 448b4c2428 4c8bc0 } // n = 4, score = 200 // e8???????? | // e8???????? | // 448b4c2428 | lea eax, [esp + 0x4e2] // 4c8bc0 | dec eax $sequence_13 = { e8???????? e8???????? 0fb78424c6040000 99 b905000000 f7f9 } // n = 6, score = 200 // e8???????? | // e8???????? | // 0fb78424c6040000 | movzx eax, word ptr [esp + 0x4c6] // 99 | cdq // b905000000 | mov ecx, 5 // f7f9 | idiv ecx $sequence_14 = { e8???????? e8???????? 488b8c2450020000 4833cc } // n = 4, score = 200 // e8???????? | // e8???????? | // 488b8c2450020000 | mov eax, eax // 4833cc | inc esp $sequence_15 = { e8???????? e8???????? 33c0 6689442440 } // n = 4, score = 200 // e8???????? | // e8???????? | // 33c0 | xor eax, eax // 6689442440 | mov word ptr [esp + 0x40], ax condition: 7 of them and filesize < 2031616 }
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