Ransomware.
rule win_void_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" 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 = "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 = { 83ec40 a1???????? 33c4 8944243c 8b442444 53 8b5c2450 } // n = 7, score = 200 // 83ec40 | sub esp, 0x40 // a1???????? | // 33c4 | xor eax, esp // 8944243c | mov dword ptr [esp + 0x3c], eax // 8b442444 | mov eax, dword ptr [esp + 0x44] // 53 | push ebx // 8b5c2450 | mov ebx, dword ptr [esp + 0x50] $sequence_1 = { 51 52 8b5608 8bc8 c1e202 e8???????? 83c408 } // n = 7, score = 200 // 51 | push ecx // 52 | push edx // 8b5608 | mov edx, dword ptr [esi + 8] // 8bc8 | mov ecx, eax // c1e202 | shl edx, 2 // e8???????? | // 83c408 | add esp, 8 $sequence_2 = { 8a4605 8bce 3a45e7 7505 c6032b eb0f e8???????? } // n = 7, score = 200 // 8a4605 | mov al, byte ptr [esi + 5] // 8bce | mov ecx, esi // 3a45e7 | cmp al, byte ptr [ebp - 0x19] // 7505 | jne 7 // c6032b | mov byte ptr [ebx], 0x2b // eb0f | jmp 0x11 // e8???????? | $sequence_3 = { 50 8d4f30 c645fc11 e8???????? 8d8da4feffff e8???????? 8d8d38020000 } // n = 7, score = 200 // 50 | push eax // 8d4f30 | lea ecx, [edi + 0x30] // c645fc11 | mov byte ptr [ebp - 4], 0x11 // e8???????? | // 8d8da4feffff | lea ecx, [ebp - 0x15c] // e8???????? | // 8d8d38020000 | lea ecx, [ebp + 0x238] $sequence_4 = { 5f 5b 33cc e8???????? 83c430 c20400 8d4c240c } // n = 7, score = 200 // 5f | pop edi // 5b | pop ebx // 33cc | xor ecx, esp // e8???????? | // 83c430 | add esp, 0x30 // c20400 | ret 4 // 8d4c240c | lea ecx, [esp + 0xc] $sequence_5 = { 3bde 0f42de 53 8bcf e8???????? 8bd6 89442414 } // n = 7, score = 200 // 3bde | cmp ebx, esi // 0f42de | cmovb ebx, esi // 53 | push ebx // 8bcf | mov ecx, edi // e8???????? | // 8bd6 | mov edx, esi // 89442414 | mov dword ptr [esp + 0x14], eax $sequence_6 = { 68???????? eb07 6a06 68???????? 8d4dd8 e8???????? 837dec10 } // n = 7, score = 200 // 68???????? | // eb07 | jmp 9 // 6a06 | push 6 // 68???????? | // 8d4dd8 | lea ecx, [ebp - 0x28] // e8???????? | // 837dec10 | cmp dword ptr [ebp - 0x14], 0x10 $sequence_7 = { 7421 83fb10 8d45d8 0f43c6 0fbe4007 50 e8???????? } // n = 7, score = 200 // 7421 | je 0x23 // 83fb10 | cmp ebx, 0x10 // 8d45d8 | lea eax, [ebp - 0x28] // 0f43c6 | cmovae eax, esi // 0fbe4007 | movsx eax, byte ptr [eax + 7] // 50 | push eax // e8???????? | condition: 7 of them and filesize < 2744320 }
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