Ransomware. Uses dropper written in JavaScript to deploy a .NET payload.
rule win_blackbyte_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" version = "1" description = "Detects win.blackbyte." 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.blackbyte" malpedia_rule_date = "20220513" malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26" malpedia_version = "20220516" 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 = { 4488ac2489000000 440fb6ac24c4000000 4488ac2488000000 440fb6ac24c5000000 4488ac2487000000 440fb6ac24c6000000 4488ac2486000000 } // n = 7, score = 200 // 4488ac2489000000 | inc esp // 440fb6ac24c4000000 | movzx ebp, byte ptr [esp + 0xa4] // 4488ac2488000000 | inc esp // 440fb6ac24c5000000 | mov byte ptr [esp + 0x6a], ch // 4488ac2487000000 | inc esp // 440fb6ac24c6000000 | mov byte ptr [esp + 0x6d], ch // 4488ac2486000000 | inc esp $sequence_1 = { b8fbffffff ffd1 488b08 4889c2 b80b000000 ffd1 488b08 } // n = 7, score = 200 // b8fbffffff | cmp esi, eax // ffd1 | jae 0x710 // 488b08 | dec eax // 4889c2 | lea eax, [0xc0e73] // b80b000000 | dec eax // ffd1 | mov ecx, ebx // 488b08 | dec eax $sequence_2 = { b8f6ffffff ffd1 488b08 4889c2 b8e9ffffff ffd1 488b08 } // n = 7, score = 200 // b8f6ffffff | mov edi, esi // ffd1 | dec esp // 488b08 | lea eax, [ebx + 1] // 4889c2 | dec esp // b8e9ffffff | cmp esi, eax // ffd1 | jae 0x18ce // 488b08 | dec eax $sequence_3 = { 7ce6 31c0 488d5c241a b937000000 e8???????? 488bac2488000000 4881c490000000 } // n = 7, score = 200 // 7ce6 | dec esp // 31c0 | mov esi, eax // 488d5c241a | dec esp // b937000000 | cmp esi, eax // e8???????? | // 488bac2488000000 | jae 0x319 // 4881c490000000 | dec eax $sequence_4 = { 4c89642418 4889542420 4889cb 488b8c24d8000000 e8???????? 48898424d8000000 48899c24d0000000 } // n = 7, score = 200 // 4c89642418 | dec eax // 4889542420 | mov dword ptr [eax], 0 // 4889cb | dec eax // 488b8c24d8000000 | lea eax, [0x18ce94] // e8???????? | // 48898424d8000000 | dec eax // 48899c24d0000000 | mov dword ptr [esp + 0x20], eax $sequence_5 = { 488b08 4889c2 b822000000 ffd1 488b08 4889c2 b8ffffffff } // n = 7, score = 200 // 488b08 | cmp eax, 2 // 4889c2 | dec eax // b822000000 | mov edi, eax // ffd1 | dec eax // 488b08 | mov esi, ecx // 4889c2 | dec eax // b8ffffffff | mov eax, dword ptr [esp + 0x40] $sequence_6 = { b801000000 ffd1 488b08 4889c2 b8edffffff ffd1 488b08 } // n = 7, score = 200 // b801000000 | mov edi, dword ptr [esp + 0x308] // ffd1 | dec eax // 488b08 | mov dword ptr [edi + 0x10], ecx // 4889c2 | dec esp // b8edffffff | mov ebx, ebx // ffd1 | dec esp // 488b08 | mov ecx, ecx $sequence_7 = { 7534 4889442418 48c744242000000000 488d7c2428 488d7ff0 48896c24f0 488d6c24f0 } // n = 7, score = 200 // 7534 | mov dword ptr [esp + 0x30], edi // 4889442418 | dec eax // 48c744242000000000 | mov dword ptr [esp + 0x48], edx // 488d7c2428 | dec eax // 488d7ff0 | mov dword ptr [esp + 0x58], esi // 48896c24f0 | xor eax, eax // 488d6c24f0 | dec ecx $sequence_8 = { 833d????????00 7506 4c890418 eb05 e8???????? 4d8d4301 4c39c1 } // n = 7, score = 200 // 833d????????00 | // 7506 | dec eax // 4c890418 | mov ebx, edi // eb05 | dec eax // e8???????? | // 4d8d4301 | mov edi, esi // 4c39c1 | dec esp $sequence_9 = { 4889c2 b806000000 ffd1 488b08 4889c2 b8faffffff ffd1 } // n = 7, score = 200 // 4889c2 | mov dword ptr [esp + 0x1a0], ebx // b806000000 | dec eax // ffd1 | mov dword ptr [esp + 0x1008], eax // 488b08 | dec eax // 4889c2 | mov dword ptr [esp + 0x228], ebx // b8faffffff | dec eax // ffd1 | mov dword ptr [esp + 0x2320], ecx condition: 7 of them and filesize < 9435136 }
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