Ransomware.
rule win_rook_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.rook." 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.rook" 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 = { 48b90000000000000080 488987c8000000 488d059f9d0200 48894718 488d05649c0200 c7470801000000 48c7471004000000 } // n = 7, score = 100 // 48b90000000000000080 | cmp eax, 1 // 488987c8000000 | dec esp // 488d059f9d0200 | mov eax, ebx // 48894718 | xor edx, edx // 488d05649c0200 | mov ecx, dword ptr [ebp + 0x26b8] // c7470801000000 | dec esp // 48c7471004000000 | mov eax, esi $sequence_1 = { 488d15e0ca0100 488bc1 83e13f 48c1f806 48c1e106 488b04c2 0fb6440838 } // n = 7, score = 100 // 488d15e0ca0100 | mov dword ptr [esp + 0x30], 0 // 488bc1 | mov dword ptr [esp + 0x20], 3 // 83e13f | dec ecx // 48c1f806 | mov ecx, ebp // 48c1e106 | dec esp // 488b04c2 | mov dword ptr [esp + 0x2758], edi // 0fb6440838 | dec ebp $sequence_2 = { 488bd3 e8???????? 4883c320 4983ee01 } // n = 4, score = 100 // 488bd3 | arpl word ptr [ebp + 0x26a8], ax // e8???????? | // 4883c320 | dec eax // 4983ee01 | cmp eax, 0x900 $sequence_3 = { 4533948da0a60500 453317 4983c704 4c897df0 44895548 8bce } // n = 6, score = 100 // 4533948da0a60500 | dec eax // 453317 | lea ecx, [ebp + 8] // 4983c704 | nop word ptr [eax + eax] // 4c897df0 | dec eax // 44895548 | mov eax, dword ptr [ecx] // 8bce | cmp word ptr [eax], 0x2d $sequence_4 = { 47338496f08c0400 448b53f8 4533d8 4533d3 418bcb c1c904 } // n = 6, score = 100 // 47338496f08c0400 | mov eax, edx // 448b53f8 | dec eax // 4533d8 | cwde // 4533d3 | mov ecx, dword ptr [edx + eax*4 + 0xa4b4] // 418bcb | dec eax // c1c904 | add ecx, edx $sequence_5 = { 488b8da0260000 ff15???????? 4c8b85a0260000 33ff } // n = 4, score = 100 // 488b8da0260000 | inc ebp // ff15???????? | // 4c8b85a0260000 | xor ebx, eax // 33ff | inc edi $sequence_6 = { c1c008 4389848c70950500 49ffc1 4983eb01 0f859dfeffff } // n = 5, score = 100 // c1c008 | or ecx, 0xffffffff // 4389848c70950500 | inc ecx // 49ffc1 | mov eax, 1 // 4983eb01 | dec ecx // 0f859dfeffff | mov edx, edi $sequence_7 = { 418bbc96a0b20500 0fb6c8 458bd8 418bda 418bc4 4133bc8ea0a20500 48c1e818 } // n = 7, score = 100 // 418bbc96a0b20500 | lea ecx, [0x1f500] // 0fb6c8 | inc ecx // 458bd8 | and edx, 0x3f // 418bda | dec ecx // 418bc4 | add ebp, eax // 4133bc8ea0a20500 | and dword ptr [ebx], 0 // 48c1e818 | dec ecx $sequence_8 = { 488b1d???????? 8d4101 488b1ccb 99 f73d???????? 488d0d3d650500 8915???????? } // n = 7, score = 100 // 488b1d???????? | // 8d4101 | mov ecx, esi // 488b1ccb | dec esp // 99 | mov esp, dword ptr [esp + 0x2d8] // f73d???????? | // 488d0d3d650500 | test eax, eax // 8915???????? | $sequence_9 = { 488d442460 4d2bc1 4889442430 488d15a5bb0400 488d0dbebb0400 4c89642420 e8???????? } // n = 7, score = 100 // 488d442460 | dec eax // 4d2bc1 | lea eax, [0x297fa] // 4889442430 | mov dword ptr [edi + 0x98], 1 // 488d15a5bb0400 | dec eax // 488d0dbebb0400 | mov dword ptr [edi + 0xa0], 3 // 4c89642420 | mov dword ptr [edi + 0x38], 1 // e8???????? | condition: 7 of them and filesize < 843776 }
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