According to Trend Micro, this is a loader for win.transbox, used by threat actor Earth Yako.
rule win_mirrorkey_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.mirrorkey." 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.mirrorkey" 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 = { 0f57c0 0f1145d8 ff15???????? c70016000000 ff15???????? 8d45d4 50 } // n = 7, score = 100 // 0f57c0 | xorps xmm0, xmm0 // 0f1145d8 | movups xmmword ptr [ebp - 0x28], xmm0 // ff15???????? | // c70016000000 | mov dword ptr [eax], 0x16 // ff15???????? | // 8d45d4 | lea eax, [ebp - 0x2c] // 50 | push eax $sequence_1 = { 895914 0fb77806 85ff 7414 8d4b10 8b4104 0301 } // n = 7, score = 100 // 895914 | mov dword ptr [ecx + 0x14], ebx // 0fb77806 | movzx edi, word ptr [eax + 6] // 85ff | test edi, edi // 7414 | je 0x16 // 8d4b10 | lea ecx, [ebx + 0x10] // 8b4104 | mov eax, dword ptr [ecx + 4] // 0301 | add eax, dword ptr [ecx] $sequence_2 = { ff15???????? 83c40c c744241000000000 33c0 c644242c00 8944242d 8d742433 } // n = 7, score = 100 // ff15???????? | // 83c40c | add esp, 0xc // c744241000000000 | mov dword ptr [esp + 0x10], 0 // 33c0 | xor eax, eax // c644242c00 | mov byte ptr [esp + 0x2c], 0 // 8944242d | mov dword ptr [esp + 0x2d], eax // 8d742433 | lea esi, [esp + 0x33] $sequence_3 = { 8bf9 8b7508 8d45a4 50 } // n = 4, score = 100 // 8bf9 | mov edi, ecx // 8b7508 | mov esi, dword ptr [ebp + 8] // 8d45a4 | lea eax, [ebp - 0x5c] // 50 | push eax $sequence_4 = { 83c004 8b7dfc 83ff01 7f87 5f } // n = 5, score = 100 // 83c004 | add eax, 4 // 8b7dfc | mov edi, dword ptr [ebp - 4] // 83ff01 | cmp edi, 1 // 7f87 | jg 0xffffff89 // 5f | pop edi $sequence_5 = { 730b 68???????? ff15???????? 894610 837e1410 } // n = 5, score = 100 // 730b | jae 0xd // 68???????? | // ff15???????? | // 894610 | mov dword ptr [esi + 0x10], eax // 837e1410 | cmp dword ptr [esi + 0x14], 0x10 $sequence_6 = { 897508 2bda ebaa 8d5aff 83c704 eba2 } // n = 6, score = 100 // 897508 | mov dword ptr [ebp + 8], esi // 2bda | sub ebx, edx // ebaa | jmp 0xffffffac // 8d5aff | lea ebx, [edx - 1] // 83c704 | add edi, 4 // eba2 | jmp 0xffffffa4 $sequence_7 = { 8d4dd8 50 e8???????? 8d4d8c e8???????? 837de808 7d15 } // n = 7, score = 100 // 8d4dd8 | lea ecx, [ebp - 0x28] // 50 | push eax // e8???????? | // 8d4d8c | lea ecx, [ebp - 0x74] // e8???????? | // 837de808 | cmp dword ptr [ebp - 0x18], 8 // 7d15 | jge 0x17 $sequence_8 = { 6a00 51 89542414 ff15???????? 83c408 83f8ff } // n = 6, score = 100 // 6a00 | push 0 // 51 | push ecx // 89542414 | mov dword ptr [esp + 0x14], edx // ff15???????? | // 83c408 | add esp, 8 // 83f8ff | cmp eax, -1 $sequence_9 = { 53 8b5d0c 894dfc 8b4d08 56 } // n = 5, score = 100 // 53 | push ebx // 8b5d0c | mov ebx, dword ptr [ebp + 0xc] // 894dfc | mov dword ptr [ebp - 4], ecx // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 56 | push esi condition: 7 of them and filesize < 117760 }
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