Ransomware written in Nim.
rule win_unidentified_088_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.unidentified_088." 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.unidentified_088" malpedia_rule_date = "20230705" malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41" malpedia_version = "20230715" 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 = { e8???????? 8b45dc 897de0 8945e4 eb3e 3b13 } // n = 6, score = 100 // e8???????? | // 8b45dc | mov eax, dword ptr [ebp - 0x24] // 897de0 | mov dword ptr [ebp - 0x20], edi // 8945e4 | mov dword ptr [ebp - 0x1c], eax // eb3e | jmp 0x40 // 3b13 | cmp edx, dword ptr [ebx] $sequence_1 = { c705????????c08c4200 c705????????00000000 c605????????02 c705????????c8014200 c705????????1c000000 c705????????04000000 } // n = 6, score = 100 // c705????????c08c4200 | // c705????????00000000 | // c605????????02 | // c705????????c8014200 | // c705????????1c000000 | // c705????????04000000 | $sequence_2 = { c3 c3 55 89c1 89e5 } // n = 5, score = 100 // c3 | ret // c3 | ret // 55 | push ebp // 89c1 | mov ecx, eax // 89e5 | mov ebp, esp $sequence_3 = { 83c8ff 8d4de4 89da e8???????? 84c0 745d e8???????? } // n = 7, score = 100 // 83c8ff | or eax, 0xffffffff // 8d4de4 | lea ecx, [ebp - 0x1c] // 89da | mov edx, ebx // e8???????? | // 84c0 | test al, al // 745d | je 0x5f // e8???????? | $sequence_4 = { 8b45dc 8b7dc4 8a540708 80fa5c 7405 80fa2f 751e } // n = 7, score = 100 // 8b45dc | mov eax, dword ptr [ebp - 0x24] // 8b7dc4 | mov edi, dword ptr [ebp - 0x3c] // 8a540708 | mov dl, byte ptr [edi + eax + 8] // 80fa5c | cmp dl, 0x5c // 7405 | je 7 // 80fa2f | cmp dl, 0x2f // 751e | jne 0x20 $sequence_5 = { 8945cc 0306 e8???????? 8d4de4 ba01000000 89f8 } // n = 6, score = 100 // 8945cc | mov dword ptr [ebp - 0x34], eax // 0306 | add eax, dword ptr [esi] // e8???????? | // 8d4de4 | lea ecx, [ebp - 0x1c] // ba01000000 | mov edx, 1 // 89f8 | mov eax, edi $sequence_6 = { 56 53 81ecfc070000 a1???????? c744240400000000 8985b8f8ffff 8d85b8f8ffff } // n = 7, score = 100 // 56 | push esi // 53 | push ebx // 81ecfc070000 | sub esp, 0x7fc // a1???????? | // c744240400000000 | mov dword ptr [esp + 4], 0 // 8985b8f8ffff | mov dword ptr [ebp - 0x748], eax // 8d85b8f8ffff | lea eax, [ebp - 0x748] $sequence_7 = { 8b5508 2b13 e9???????? 894de0 e8???????? 394508 0f4d4508 } // n = 7, score = 100 // 8b5508 | mov edx, dword ptr [ebp + 8] // 2b13 | sub edx, dword ptr [ebx] // e9???????? | // 894de0 | mov dword ptr [ebp - 0x20], ecx // e8???????? | // 394508 | cmp dword ptr [ebp + 8], eax // 0f4d4508 | cmovge eax, dword ptr [ebp + 8] $sequence_8 = { c21000 55 b9???????? 89e5 83ec08 e8???????? b9???????? } // n = 7, score = 100 // c21000 | ret 0x10 // 55 | push ebp // b9???????? | // 89e5 | mov ebp, esp // 83ec08 | sub esp, 8 // e8???????? | // b9???????? | $sequence_9 = { 8945b0 8d45c0 e8???????? 8b03 } // n = 4, score = 100 // 8945b0 | mov dword ptr [ebp - 0x50], eax // 8d45c0 | lea eax, [ebp - 0x40] // e8???????? | // 8b03 | mov eax, dword ptr [ebx] condition: 7 of them and filesize < 919552 }
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