Ransomware.
rule win_yakuza_ransomware_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" 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 = "20231130" malpedia_hash = "fc8a0e9f343f6d6ded9e7df1a64dac0cc68d7351" malpedia_version = "20230808" 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 = { 8bd1 d1ea b8ffffff1f 2bc2 3bc8 7607 8bc3 } // n = 7, score = 100 // 8bd1 | mov edx, ecx // d1ea | shr edx, 1 // b8ffffff1f | mov eax, 0x1fffffff // 2bc2 | sub eax, edx // 3bc8 | cmp ecx, eax // 7607 | jbe 9 // 8bc3 | mov eax, ebx $sequence_1 = { e8???????? 3b780c 730e 8b4008 8b34b8 85f6 0f85d7000000 } // n = 7, score = 100 // e8???????? | // 3b780c | cmp edi, dword ptr [eax + 0xc] // 730e | jae 0x10 // 8b4008 | mov eax, dword ptr [eax + 8] // 8b34b8 | mov esi, dword ptr [eax + edi*4] // 85f6 | test esi, esi // 0f85d7000000 | jne 0xdd $sequence_2 = { d1f8 837e1408 7202 8b36 50 ff7508 8bce } // n = 7, score = 100 // d1f8 | sar eax, 1 // 837e1408 | cmp dword ptr [esi + 0x14], 8 // 7202 | jb 4 // 8b36 | mov esi, dword ptr [esi] // 50 | push eax // ff7508 | push dword ptr [ebp + 8] // 8bce | mov ecx, esi $sequence_3 = { 6a01 6a01 57 8d4d80 e8???????? 8b4580 8d4d80 } // n = 7, score = 100 // 6a01 | push 1 // 6a01 | push 1 // 57 | push edi // 8d4d80 | lea ecx, [ebp - 0x80] // e8???????? | // 8b4580 | mov eax, dword ptr [ebp - 0x80] // 8d4d80 | lea ecx, [ebp - 0x80] $sequence_4 = { 8d7018 83c030 8b11 03c7 50 03f7 56 } // n = 7, score = 100 // 8d7018 | lea esi, [eax + 0x18] // 83c030 | add eax, 0x30 // 8b11 | mov edx, dword ptr [ecx] // 03c7 | add eax, edi // 50 | push eax // 03f7 | add esi, edi // 56 | push esi $sequence_5 = { c745fcffffffff 56 8b4de0 41 51 53 8bcf } // n = 7, score = 100 // c745fcffffffff | mov dword ptr [ebp - 4], 0xffffffff // 56 | push esi // 8b4de0 | mov ecx, dword ptr [ebp - 0x20] // 41 | inc ecx // 51 | push ecx // 53 | push ebx // 8bcf | mov ecx, edi $sequence_6 = { 8b4f14 8b5614 85c9 743e 85c0 750d e8???????? } // n = 7, score = 100 // 8b4f14 | mov ecx, dword ptr [edi + 0x14] // 8b5614 | mov edx, dword ptr [esi + 0x14] // 85c9 | test ecx, ecx // 743e | je 0x40 // 85c0 | test eax, eax // 750d | jne 0xf // e8???????? | $sequence_7 = { eb17 0fb74644 8d4e24 50 e8???????? 6a2d 8d4e24 } // n = 7, score = 100 // eb17 | jmp 0x19 // 0fb74644 | movzx eax, word ptr [esi + 0x44] // 8d4e24 | lea ecx, [esi + 0x24] // 50 | push eax // e8???????? | // 6a2d | push 0x2d // 8d4e24 | lea ecx, [esi + 0x24] $sequence_8 = { 8b06 6a02 51 53 8d8d50ffffff 51 8bce } // n = 7, score = 100 // 8b06 | mov eax, dword ptr [esi] // 6a02 | push 2 // 51 | push ecx // 53 | push ebx // 8d8d50ffffff | lea ecx, [ebp - 0xb0] // 51 | push ecx // 8bce | mov ecx, esi $sequence_9 = { c745f000000000 c7461000000000 c7461407000000 668906 8945fc 8bc3 c745f001000000 } // n = 7, score = 100 // c745f000000000 | mov dword ptr [ebp - 0x10], 0 // c7461000000000 | mov dword ptr [esi + 0x10], 0 // c7461407000000 | mov dword ptr [esi + 0x14], 7 // 668906 | mov word ptr [esi], ax // 8945fc | mov dword ptr [ebp - 4], eax // 8bc3 | mov eax, ebx // c745f001000000 | mov dword ptr [ebp - 0x10], 1 condition: 7 of them and filesize < 2811904 }
If your designated proposal does not fit in any other category, feel free to write a free-text in the comment field below. Changes regarding references should be proposed on the Malpedia library page.
Your suggestion will be reviewed before being published. Thank you for contributing!
YYYY-MM-DD
YYYY-MM
YYYY