rule win_koiloader_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-09-17"
        version = "1"
        description = "Detects win.koiloader."
        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.koiloader"
        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 = { ff15???????? 85c0 0f84b9020000 6a00 6880000000 6a02 6a00 }
            // n = 7, score = 600
            //   ff15????????         |                     
            //   85c0                 | test                eax, eax
            //   0f84b9020000         | je                  0x2bf
            //   6a00                 | push                0
            //   6880000000           | push                0x80
            //   6a02                 | push                2
            //   6a00                 | push                0

        $sequence_1 = { 8d55f4 8b45f8 bb01000000 52 56 }
            // n = 5, score = 600
            //   8d55f4               | lea                 edx, [ebp - 0xc]
            //   8b45f8               | mov                 eax, dword ptr [ebp - 8]
            //   bb01000000           | mov                 ebx, 1
            //   52                   | push                edx
            //   56                   | push                esi

        $sequence_2 = { 68???????? c6041900 668b4508 6a00 6a00 }
            // n = 5, score = 600
            //   68????????           |                     
            //   c6041900             | mov                 byte ptr [ecx + ebx], 0
            //   668b4508             | mov                 ax, word ptr [ebp + 8]
            //   6a00                 | push                0
            //   6a00                 | push                0

        $sequence_3 = { 56 ff15???????? 68???????? 56 8b35???????? 8945c8 ffd6 }
            // n = 7, score = 600
            //   56                   | push                esi
            //   ff15????????         |                     
            //   68????????           |                     
            //   56                   | push                esi
            //   8b35????????         |                     
            //   8945c8               | mov                 dword ptr [ebp - 0x38], eax
            //   ffd6                 | call                esi

        $sequence_4 = { 8d8548fdffff 50 6a00 68e9fd0000 ffd7 8945f0 }
            // n = 6, score = 600
            //   8d8548fdffff         | lea                 eax, [ebp - 0x2b8]
            //   50                   | push                eax
            //   6a00                 | push                0
            //   68e9fd0000           | push                0xfde9
            //   ffd7                 | call                edi
            //   8945f0               | mov                 dword ptr [ebp - 0x10], eax

        $sequence_5 = { 68???????? 83c140 51 57 ff15???????? 83c414 8d4d9c }
            // n = 7, score = 600
            //   68????????           |                     
            //   83c140               | add                 ecx, 0x40
            //   51                   | push                ecx
            //   57                   | push                edi
            //   ff15????????         |                     
            //   83c414               | add                 esp, 0x14
            //   8d4d9c               | lea                 ecx, [ebp - 0x64]

        $sequence_6 = { ffd7 85c0 7513 68???????? 8d4598 50 ffd7 }
            // n = 7, score = 600
            //   ffd7                 | call                edi
            //   85c0                 | test                eax, eax
            //   7513                 | jne                 0x15
            //   68????????           |                     
            //   8d4598               | lea                 eax, [ebp - 0x68]
            //   50                   | push                eax
            //   ffd7                 | call                edi

        $sequence_7 = { ff15???????? 8945fc 85c0 741a 6a00 6a00 ff75f0 }
            // n = 7, score = 600
            //   ff15????????         |                     
            //   8945fc               | mov                 dword ptr [ebp - 4], eax
            //   85c0                 | test                eax, eax
            //   741a                 | je                  0x1c
            //   6a00                 | push                0
            //   6a00                 | push                0
            //   ff75f0               | push                dword ptr [ebp - 0x10]

        $sequence_8 = { 897dcc 8bcb e8???????? 6905????????e8030000 8b35???????? 50 }
            // n = 6, score = 600
            //   897dcc               | mov                 dword ptr [ebp - 0x34], edi
            //   8bcb                 | mov                 ecx, ebx
            //   e8????????           |                     
            //   6905????????e8030000     |     
            //   8b35????????         |                     
            //   50                   | push                eax

        $sequence_9 = { 8a0c8550124000 40 d3c2 8b4de4 03f2 8b55ec 83c203 }
            // n = 7, score = 600
            //   8a0c8550124000       | mov                 cl, byte ptr [eax*4 + 0x401250]
            //   40                   | inc                 eax
            //   d3c2                 | rol                 edx, cl
            //   8b4de4               | mov                 ecx, dword ptr [ebp - 0x1c]
            //   03f2                 | add                 esi, edx
            //   8b55ec               | mov                 edx, dword ptr [ebp - 0x14]
            //   83c203               | add                 edx, 3

    condition:
        7 of them and filesize < 101376
}