Ransomware.
rule win_yakuza_ransomware_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.yakuza_ransomware." 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.yakuza_ransomware" 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???????? 8d45b0 50 8d4be0 e8???????? 8b4dbc 394db8 } // n = 7, score = 100 // e8???????? | // 8d45b0 | lea eax, [ebp - 0x50] // 50 | push eax // 8d4be0 | lea ecx, [ebx - 0x20] // e8???????? | // 8b4dbc | mov ecx, dword ptr [ebp - 0x44] // 394db8 | cmp dword ptr [ebp - 0x48], ecx $sequence_1 = { e9???????? 8d8dd0fbffff e9???????? 8b8de0fbffff 83c104 e9???????? 8d8dc8feffff } // n = 7, score = 100 // e9???????? | // 8d8dd0fbffff | lea ecx, [ebp - 0x430] // e9???????? | // 8b8de0fbffff | mov ecx, dword ptr [ebp - 0x420] // 83c104 | add ecx, 4 // e9???????? | // 8d8dc8feffff | lea ecx, [ebp - 0x138] $sequence_2 = { eb05 e8???????? 50 8d8d98feffff e8???????? 8d8598feffff c645fc22 } // n = 7, score = 100 // eb05 | jmp 7 // e8???????? | // 50 | push eax // 8d8d98feffff | lea ecx, [ebp - 0x168] // e8???????? | // 8d8598feffff | lea eax, [ebp - 0x168] // c645fc22 | mov byte ptr [ebp - 4], 0x22 $sequence_3 = { e8???????? 83c40c 8945e4 85c0 0f84f2000000 8bc6 8d7008 } // n = 7, score = 100 // e8???????? | // 83c40c | add esp, 0xc // 8945e4 | mov dword ptr [ebp - 0x1c], eax // 85c0 | test eax, eax // 0f84f2000000 | je 0xf8 // 8bc6 | mov eax, esi // 8d7008 | lea esi, [eax + 8] $sequence_4 = { e8???????? 6a00 6a00 56 68???????? 6800000200 6a00 } // n = 7, score = 100 // e8???????? | // 6a00 | push 0 // 6a00 | push 0 // 56 | push esi // 68???????? | // 6800000200 | push 0x20000 // 6a00 | push 0 $sequence_5 = { e8???????? 83c618 83c404 3bf3 75ee 8b37 8b4708 } // n = 7, score = 100 // e8???????? | // 83c618 | add esi, 0x18 // 83c404 | add esp, 4 // 3bf3 | cmp esi, ebx // 75ee | jne 0xfffffff0 // 8b37 | mov esi, dword ptr [edi] // 8b4708 | mov eax, dword ptr [edi + 8] $sequence_6 = { eb05 1bc0 83c801 85c0 0f85ee000000 f6460801 0f848a000000 } // n = 7, score = 100 // eb05 | jmp 7 // 1bc0 | sbb eax, eax // 83c801 | or eax, 1 // 85c0 | test eax, eax // 0f85ee000000 | jne 0xf4 // f6460801 | test byte ptr [esi + 8], 1 // 0f848a000000 | je 0x90 $sequence_7 = { e8???????? 6a30 56 8d4dbc e8???????? c745bc18424d00 c745c0d0424d00 } // n = 7, score = 100 // e8???????? | // 6a30 | push 0x30 // 56 | push esi // 8d4dbc | lea ecx, [ebp - 0x44] // e8???????? | // c745bc18424d00 | mov dword ptr [ebp - 0x44], 0x4d4218 // c745c0d0424d00 | mov dword ptr [ebp - 0x40], 0x4d42d0 $sequence_8 = { 8d8d1cffffff e9???????? 8d4ddc e9???????? 8d8d7cffffff e9???????? 8d8d00ffffff } // n = 7, score = 100 // 8d8d1cffffff | lea ecx, [ebp - 0xe4] // e9???????? | // 8d4ddc | lea ecx, [ebp - 0x24] // e9???????? | // 8d8d7cffffff | lea ecx, [ebp - 0x84] // e9???????? | // 8d8d00ffffff | lea ecx, [ebp - 0x100] $sequence_9 = { 0fb6c8 8b470c f6044848 7509 c745fcffffffff eb36 8b06 } // n = 7, score = 100 // 0fb6c8 | movzx ecx, al // 8b470c | mov eax, dword ptr [edi + 0xc] // f6044848 | test byte ptr [eax + ecx*2], 0x48 // 7509 | jne 0xb // c745fcffffffff | mov dword ptr [ebp - 4], 0xffffffff // eb36 | jmp 0x38 // 8b06 | mov eax, dword ptr [esi] condition: 7 of them and filesize < 2811904 }
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