Ransomware.
rule win_void_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.void." 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.void" 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 = { ff504c ff742418 8bf8 ff742418 8bcf ff742424 8b17 } // n = 7, score = 200 // ff504c | call dword ptr [eax + 0x4c] // ff742418 | push dword ptr [esp + 0x18] // 8bf8 | mov edi, eax // ff742418 | push dword ptr [esp + 0x18] // 8bcf | mov ecx, edi // ff742424 | push dword ptr [esp + 0x24] // 8b17 | mov edx, dword ptr [edi] $sequence_1 = { eb06 8bb56cfbffff 6a0e 68???????? 8d8dd8fbffff c785e8fbffff00000000 } // n = 6, score = 200 // eb06 | jmp 8 // 8bb56cfbffff | mov esi, dword ptr [ebp - 0x494] // 6a0e | push 0xe // 68???????? | // 8d8dd8fbffff | lea ecx, [ebp - 0x428] // c785e8fbffff00000000 | mov dword ptr [ebp - 0x418], 0 $sequence_2 = { 8bf1 8b6f0c 8b460c 3be8 762e 6a01 55 } // n = 7, score = 200 // 8bf1 | mov esi, ecx // 8b6f0c | mov ebp, dword ptr [edi + 0xc] // 8b460c | mov eax, dword ptr [esi + 0xc] // 3be8 | cmp ebp, eax // 762e | jbe 0x30 // 6a01 | push 1 // 55 | push ebp $sequence_3 = { 8bd0 89442454 8b84248c000000 8bc8 c1c007 c1c90b 33c8 } // n = 7, score = 200 // 8bd0 | mov edx, eax // 89442454 | mov dword ptr [esp + 0x54], eax // 8b84248c000000 | mov eax, dword ptr [esp + 0x8c] // 8bc8 | mov ecx, eax // c1c007 | rol eax, 7 // c1c90b | ror ecx, 0xb // 33c8 | xor ecx, eax $sequence_4 = { ff5004 8d4584 c745fc00000000 50 e8???????? 8b4d88 83c404 } // n = 7, score = 200 // ff5004 | call dword ptr [eax + 4] // 8d4584 | lea eax, [ebp - 0x7c] // c745fc00000000 | mov dword ptr [ebp - 4], 0 // 50 | push eax // e8???????? | // 8b4d88 | mov ecx, dword ptr [ebp - 0x78] // 83c404 | add esp, 4 $sequence_5 = { 7f0e 7c08 8b4508 3b4510 7704 b001 5d } // n = 7, score = 200 // 7f0e | jg 0x10 // 7c08 | jl 0xa // 8b4508 | mov eax, dword ptr [ebp + 8] // 3b4510 | cmp eax, dword ptr [ebp + 0x10] // 7704 | ja 6 // b001 | mov al, 1 // 5d | pop ebp $sequence_6 = { e8???????? 8a45d7 83c408 84c0 0f8490000000 68???????? e8???????? } // n = 7, score = 200 // e8???????? | // 8a45d7 | mov al, byte ptr [ebp - 0x29] // 83c408 | add esp, 8 // 84c0 | test al, al // 0f8490000000 | je 0x96 // 68???????? | // e8???????? | $sequence_7 = { c3 8d8dd8fbffff e9???????? 8d8dc0fbffff e9???????? 8b542408 } // n = 6, score = 200 // c3 | ret // 8d8dd8fbffff | lea ecx, [ebp - 0x428] // e9???????? | // 8d8dc0fbffff | lea ecx, [ebp - 0x440] // e9???????? | // 8b542408 | mov edx, dword ptr [esp + 8] $sequence_8 = { 740b 8d4da0 83e3fd e8???????? f6c301 7408 8d4d88 } // n = 7, score = 200 // 740b | je 0xd // 8d4da0 | lea ecx, [ebp - 0x60] // 83e3fd | and ebx, 0xfffffffd // e8???????? | // f6c301 | test bl, 1 // 7408 | je 0xa // 8d4d88 | lea ecx, [ebp - 0x78] $sequence_9 = { 8d4f10 c745ec00000000 c745f000000000 c745f400000000 c745f800000000 e8???????? } // n = 6, score = 200 // 8d4f10 | lea ecx, [edi + 0x10] // c745ec00000000 | mov dword ptr [ebp - 0x14], 0 // c745f000000000 | mov dword ptr [ebp - 0x10], 0 // c745f400000000 | mov dword ptr [ebp - 0xc], 0 // c745f800000000 | mov dword ptr [ebp - 8], 0 // e8???????? | condition: 7 of them and filesize < 2744320 }
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