Ransomware written in Go.
rule win_decaf_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.decaf." 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.decaf" 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 = { e9???????? 4983f802 7548 4c8d4301 4c39c6 7331 488d05d3a10e00 } // n = 7, score = 100 // e9???????? | // 4983f802 | dec eax // 7548 | lea ebx, [0x16949d] // 4c8d4301 | nop dword ptr [eax] // 4c39c6 | dec eax // 7331 | mov ebx, eax // 488d05d3a10e00 | dec eax $sequence_1 = { 4889f1 e8???????? 4489d0 b902000000 e8???????? 4489c0 b902000000 } // n = 7, score = 100 // 4889f1 | inc esp // e8???????? | // 4489d0 | movzx ebp, byte ptr [esp + 0x68] // b902000000 | inc esp // e8???????? | // 4489c0 | mov byte ptr [esp + 0x47], ch // b902000000 | inc esp $sequence_2 = { e8???????? 4889442428 48c70000000000 488d0534a90d00 e8???????? 4889442420 488d0503f20e00 } // n = 7, score = 100 // e8???????? | // 4889442428 | mov dword ptr [esp + 0x80], eax // 48c70000000000 | mov byte ptr [esp + 0x47], 1 // 488d0534a90d00 | dec eax // e8???????? | // 4889442420 | mov ecx, dword ptr [esp + 0x98] // 488d0503f20e00 | dec eax $sequence_3 = { e8???????? 488d3d437a1f00 e8???????? e8???????? 48898424080e0000 48899c24a00b0000 488b0d???????? } // n = 7, score = 100 // e8???????? | // 488d3d437a1f00 | lea ebx, [0xba741] // e8???????? | // e8???????? | // 48898424080e0000 | dec eax // 48899c24a00b0000 | mov ecx, dword ptr [esp + 0xf0] // 488b0d???????? | $sequence_4 = { 488bbc24b0000000 48897818 488bbc24e0000000 48897828 4c8b8424a8000000 4c894030 eb37 } // n = 7, score = 100 // 488bbc24b0000000 | xor edx, eax // 48897818 | mov byte ptr [eax + 0xf], dl // 488bbc24e0000000 | movzx edx, byte ptr [esp + 0x5d] // 48897828 | inc esp // 4c8b8424a8000000 | xor edx, eax // 4c894030 | mov byte ptr [eax + 0xe], dl // eb37 | movzx edx, byte ptr [esp + 0x54] $sequence_5 = { 488b8c24e0030000 e8???????? 488d3d7b331c00 e8???????? e8???????? 48898424e8030000 48899c24f8000000 } // n = 7, score = 100 // 488b8c24e0030000 | xor edx, eax // e8???????? | // 488d3d7b331c00 | mov byte ptr [eax + 0x16], dl // e8???????? | // e8???????? | // 48898424e8030000 | movzx edx, byte ptr [esp + 0x4d] // 48899c24f8000000 | inc esp $sequence_6 = { b900001000 0f1f440000 e8???????? b900001000 e8???????? 488d05ce0a1900 bb11000000 } // n = 7, score = 100 // b900001000 | dec eax // 0f1f440000 | mov ebx, dword ptr [esp + 0xf8] // e8???????? | // b900001000 | dec eax // e8???????? | // 488d05ce0a1900 | test edx, edx // bb11000000 | jg 0x921 $sequence_7 = { eb1c 4889c7 488b8c2410130000 e8???????? 488d3db3ac1f00 e8???????? e8???????? } // n = 7, score = 100 // eb1c | dec eax // 4889c7 | lea ecx, [0x157585] // 488b8c2410130000 | dec eax // e8???????? | // 488d3db3ac1f00 | mov dword ptr [eax + 8], ecx // e8???????? | // e8???????? | $sequence_8 = { b8b7ffffff ffd1 488b08 4889c2 b866000000 ffd1 488b08 } // n = 7, score = 100 // b8b7ffffff | dec eax // ffd1 | mov dword ptr [eax], ecx // 488b08 | dec eax // 4889c2 | mov ecx, dword ptr [esp + 0xad8] // b866000000 | dec eax // ffd1 | mov dword ptr [eax + 8], ecx // 488b08 | jne 0x9b7 $sequence_9 = { e8???????? 4889842440160000 48899c24d0040000 488b0d???????? 48898c24f01f0000 488d0543f00b00 0f1f00 } // n = 7, score = 100 // e8???????? | // 4889842440160000 | mov ecx, ebx // 48899c24d0040000 | dec eax // 488b0d???????? | // 48898c24f01f0000 | mov ebx, edi // 488d0543f00b00 | dec eax // 0f1f00 | mov edi, esi condition: 7 of them and filesize < 7193600 }
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