Mandiant associates this with UNC4191, this malware spreads to removable drives.
rule win_darkdew_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.darkdew." 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.darkdew" 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 = { ff75b4 83f910 8db504ffffff 8d043b 0f43b504ffffff 898514ffffff 8d041e } // n = 7, score = 100 // ff75b4 | push dword ptr [ebp - 0x4c] // 83f910 | cmp ecx, 0x10 // 8db504ffffff | lea esi, [ebp - 0xfc] // 8d043b | lea eax, [ebx + edi] // 0f43b504ffffff | cmovae esi, dword ptr [ebp - 0xfc] // 898514ffffff | mov dword ptr [ebp - 0xec], eax // 8d041e | lea eax, [esi + ebx] $sequence_1 = { b991000000 03f0 f3a5 8b75fc 8dbd64fbffff 81c688040000 b991000000 } // n = 7, score = 100 // b991000000 | mov ecx, 0x91 // 03f0 | add esi, eax // f3a5 | rep movsd dword ptr es:[edi], dword ptr [esi] // 8b75fc | mov esi, dword ptr [ebp - 4] // 8dbd64fbffff | lea edi, [ebp - 0x49c] // 81c688040000 | add esi, 0x488 // b991000000 | mov ecx, 0x91 $sequence_2 = { 8b4d08 83f801 7419 81c244020000 8955fc 3bd1 } // n = 6, score = 100 // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 83f801 | cmp eax, 1 // 7419 | je 0x1b // 81c244020000 | add edx, 0x244 // 8955fc | mov dword ptr [ebp - 4], edx // 3bd1 | cmp edx, ecx $sequence_3 = { 56 57 8b7d08 e9???????? 8b1f 8d049da8f50110 8b30 } // n = 7, score = 100 // 56 | push esi // 57 | push edi // 8b7d08 | mov edi, dword ptr [ebp + 8] // e9???????? | // 8b1f | mov ebx, dword ptr [edi] // 8d049da8f50110 | lea eax, [ebx*4 + 0x1001f5a8] // 8b30 | mov esi, dword ptr [eax] $sequence_4 = { 8845d4 e8???????? 8bfb c645fc17 8d4f01 8a07 } // n = 6, score = 100 // 8845d4 | mov byte ptr [ebp - 0x2c], al // e8???????? | // 8bfb | mov edi, ebx // c645fc17 | mov byte ptr [ebp - 4], 0x17 // 8d4f01 | lea ecx, [edi + 1] // 8a07 | mov al, byte ptr [edi] $sequence_5 = { 8bf0 3b542420 72e2 83fb08 } // n = 4, score = 100 // 8bf0 | mov esi, eax // 3b542420 | cmp edx, dword ptr [esp + 0x20] // 72e2 | jb 0xffffffe4 // 83fb08 | cmp ebx, 8 $sequence_6 = { 6bd738 8b0c8da0f30110 c644112800 85f6 } // n = 4, score = 100 // 6bd738 | imul edx, edi, 0x38 // 8b0c8da0f30110 | mov ecx, dword ptr [ecx*4 + 0x1001f3a0] // c644112800 | mov byte ptr [ecx + edx + 0x28], 0 // 85f6 | test esi, esi $sequence_7 = { 0fbe8070e10110 40 8945cc 2b45dc 8945d4 3bc2 0f8f10020000 } // n = 7, score = 100 // 0fbe8070e10110 | movsx eax, byte ptr [eax + 0x1001e170] // 40 | inc eax // 8945cc | mov dword ptr [ebp - 0x34], eax // 2b45dc | sub eax, dword ptr [ebp - 0x24] // 8945d4 | mov dword ptr [ebp - 0x2c], eax // 3bc2 | cmp eax, edx // 0f8f10020000 | jg 0x216 $sequence_8 = { 8bc6 8bcf 2b4c2428 83c408 } // n = 4, score = 100 // 8bc6 | mov eax, esi // 8bcf | mov ecx, edi // 2b4c2428 | sub ecx, dword ptr [esp + 0x28] // 83c408 | add esp, 8 $sequence_9 = { b991000000 894508 8dbda8fdffff 8bf0 8d8574fcffff 50 8d85b8feffff } // n = 7, score = 100 // b991000000 | mov ecx, 0x91 // 894508 | mov dword ptr [ebp + 8], eax // 8dbda8fdffff | lea edi, [ebp - 0x258] // 8bf0 | mov esi, eax // 8d8574fcffff | lea eax, [ebp - 0x38c] // 50 | push eax // 8d85b8feffff | lea eax, [ebp - 0x148] condition: 7 of them and filesize < 279552 }
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