A family identified by ESET Research in the InvisiMole campaign.
rule win_rc2fm_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.rc2fm." 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.rc2fm" 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 = { 48894c2408 55 57 4154 4156 488d6c24c1 4881ecb8000000 } // n = 7, score = 100 // 48894c2408 | inc ecx // 55 | cmp dword ptr [edx + 0x40], 2 // 57 | dec eax // 4154 | mov ebp, edx // 4156 | dec eax // 488d6c24c1 | mov ebx, ecx // 4881ecb8000000 | dec eax $sequence_1 = { 4883ec20 498bf1 4d8bf0 4c8bfa 488bd9 ff15???????? } // n = 6, score = 100 // 4883ec20 | mov edx, 0x40003 // 498bf1 | je 0x958 // 4d8bf0 | cmp eax, -1 // 4c8bfa | je 0x970 // 488bd9 | inc esp // ff15???????? | $sequence_2 = { 415c 5f 5b c3 488b09 4889ac2480000000 } // n = 6, score = 100 // 415c | dec esp // 5f | mov esi, edx // 5b | dec esp // c3 | mov dword ptr [esp + 0x30], edi // 488b09 | inc ebp // 4889ac2480000000 | xor esi, esi $sequence_3 = { b001 eb14 448bc3 ba00000500 b91b000100 e8???????? } // n = 6, score = 100 // b001 | inc eax // eb14 | movzx eax, ch // 448bc3 | dec eax // ba00000500 | add esp, 0x30 // b91b000100 | inc ecx // e8???????? | $sequence_4 = { 488b4808 4c897d00 4c89742460 48894df8 8d4e14 e8???????? 6690 } // n = 7, score = 100 // 488b4808 | xor esi, esi // 4c897d00 | dec eax // 4c89742460 | mov esi, ecx // 48894df8 | dec eax // 8d4e14 | mov ebx, edx // e8???????? | // 6690 | dec esp $sequence_5 = { 448bc0 e8???????? eb0f ba0a000b00 b911000100 e8???????? 488b0d???????? } // n = 7, score = 100 // 448bc0 | mov esi, dword ptr [esp + 0x30] // e8???????? | // eb0f | xor al, al // ba0a000b00 | dec esp // b911000100 | mov eax, edi // e8???????? | // 488b0d???????? | $sequence_6 = { 0fb68c28304c0200 eb0c 48c1e807 0fb68c28304d0200 4863c1 448bd7 66ff8483b0090000 } // n = 7, score = 100 // 0fb68c28304c0200 | dec eax // eb0c | lea edi, [ecx*8] // 48c1e807 | dec edx // 0fb68c28304d0200 | mov ecx, dword ptr [edi + ecx + 0x10] // 4863c1 | dec eax // 448bd7 | arpl cx, ax // 66ff8483b0090000 | dec eax $sequence_7 = { 88040a ff4328 8b5328 0fb64745 488b4b10 88040a ff4328 } // n = 7, score = 100 // 88040a | mov byte ptr [esp + 0x2c], bh // ff4328 | cpuid // 8b5328 | mov dword ptr [esp + 0x24], ecx // 0fb64745 | mov dword ptr [esp + 0x28], edx // 488b4b10 | mov dword ptr [esp + 0x20], eax // 88040a | mov eax, 0x400 // ff4328 | dec eax $sequence_8 = { 83b98804000000 488bd9 7431 ff8b88040000 8b8388040000 4c8b84c360040000 4d85c0 } // n = 7, score = 100 // 83b98804000000 | mov esp, esi // 488bd9 | mov dword ptr [edi], eax // 7431 | jmp 0x883 // ff8b88040000 | inc esp // 8b8388040000 | mov eax, eax // 4c8b84c360040000 | mov edx, 0x20006 // 4d85c0 | mov eax, dword ptr [ebp + 7] $sequence_9 = { 0f8781010000 83fd09 0f8778010000 448b642478 4183fc04 0f8769010000 488b4938 } // n = 7, score = 100 // 0f8781010000 | je 0xce1 // 83fd09 | dec eax // 0f8778010000 | mov ecx, edx // 448b642478 | dec eax // 4183fc04 | sub ebx, edx // 0f8769010000 | inc ebp // 488b4938 | mov eax, ecx condition: 7 of them and filesize < 410624 }
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