rule win_rc2fm_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-09-17"
        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 = "20260916"
        malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6"
        malpedia_version = "20260917"
        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 = { 48898424b8000000 4883f8ff 0f842d010000 4c8d8c2408010000 488d542440 41b805000000 }
            // n = 6, score = 100
            //   48898424b8000000     | mov                 eax, dword ptr [ebp + 0x18]
            //   4883f8ff             | mov                 edx, dword ptr [esi]
            //   0f842d010000         | dec                 eax
            //   4c8d8c2408010000     | mov                 ecx, dword ptr [ebx + 0x10]
            //   488d542440           | dec                 esp
            //   41b805000000         | lea                 eax, [ebp + 4]

        $sequence_1 = { ff15???????? 4885db 75e5 4d896610 4d896608 458926 400fb6c5 }
            // n = 7, score = 100
            //   ff15????????         |                     
            //   4885db               | cmp                 eax, 0xb7
            //   75e5                 | je                  0x468
            //   4d896610             | dec                 eax
            //   4d896608             | lea                 ecx, [esp + 0x50]
            //   458926               | mov                 edx, 8
            //   400fb6c5             | je                  0x4a6

        $sequence_2 = { 488d5558 488b01 ff5028 85c0 0f8831020000 488b4dc0 488d5540 }
            // n = 7, score = 100
            //   488d5558             | jne                 1
            //   488b01               | nop                 word ptr [eax + eax]
            //   ff5028               | inc                 eax
            //   85c0                 | xor                 dh, dh
            //   0f8831020000         | mov                 edi, eax
            //   488b4dc0             | test                eax, eax
            //   488d5540             | je                  0x55c

        $sequence_3 = { 4883c210 453bc3 72ec eb03 40b701 49ffca 75c7 }
            // n = 7, score = 100
            //   4883c210             | je                  0x169f
            //   453bc3               | lea                 edx, [ebx + 8]
            //   72ec                 | dec                 ecx
            //   eb03                 | mov                 ecx, ebp
            //   40b701               | dec                 eax
            //   49ffca               | mov                 edi, eax
            //   75c7                 | dec                 eax

        $sequence_4 = { 488b12 488be9 4883c12c 4532ff ff15???????? 33ff 85c0 }
            // n = 7, score = 100
            //   488b12               | inc                 dx
            //   488be9               | mov                 dword ptr [eax + ecx], esi
            //   4883c12c             | add                 dword ptr [edi], 2
            //   4532ff               | mov                 eax, dword ptr [edi]
            //   ff15????????         |                     
            //   33ff                 | inc                 esi
            //   85c0                 | mov                 dword ptr [eax + ecx], esp

        $sequence_5 = { 33d2 83c102 ffc0 f7f1 895334 4084ed 7415 }
            // n = 7, score = 100
            //   33d2                 | push                edi
            //   83c102               | dec                 eax
            //   ffc0                 | sub                 esp, 0x30
            //   f7f1                 | dec                 eax
            //   895334               | lea                 eax, [esp + 0x58]
            //   4084ed               | dec                 eax
            //   7415                 | mov                 dword ptr [esp + 8], ebx

        $sequence_6 = { 413baf20020000 0f824affffff eb15 448bc6 ba00000a00 b91b000100 e8???????? }
            // n = 7, score = 100
            //   413baf20020000       | dec                 eax
            //   0f824affffff         | dec                 eax
            //   eb15                 | xor                 edx, edx
            //   448bc6               | mov                 edx, 0x10005
            //   ba00000a00           | mov                 ecx, 0x15
            //   b91b000100           | xor                 edx, edx
            //   e8????????           |                     

        $sequence_7 = { 56 4154 4156 4157 4883ec70 8b9c24c0000000 8bac24e0000000 }
            // n = 7, score = 100
            //   56                   | jmp                 0xf8d
            //   4154                 | mov                 edx, 0x40001
            //   4156                 | test                eax, eax
            //   4157                 | je                  0xf7a
            //   4883ec70             | inc                 ecx
            //   8b9c24c0000000       | mov                 dh, 1
            //   8bac24e0000000       | jmp                 0xf93

        $sequence_8 = { 448be0 0f1f840000000000 410fb70476 6683f83a 7521 4084ff 0f8441010000 }
            // n = 7, score = 100
            //   448be0               | movzx               eax, byte ptr [esi + ecx + 8]
            //   0f1f840000000000     | dec                 eax
            //   410fb70476           | lea                 ecx, [ecx + 1]
            //   6683f83a             | mov                 byte ptr [ecx - 1], al
            //   7521                 | dec                 eax
            //   4084ff               | mov                 ecx, eax
            //   0f8441010000         | dec                 eax

        $sequence_9 = { 4032ff 84c9 7459 488d542438 488d4c2440 e8???????? }
            // n = 6, score = 100
            //   4032ff               | mov                 ecx, eax
            //   84c9                 | dec                 esp
            //   7459                 | mov                 ebp, eax
            //   488d542438           | dec                 eax
            //   488d4c2440           | mov                 dword ptr [esp + 0xc0], eax
            //   e8????????           |                     

    condition:
        7 of them and filesize < 410624
}