rule win_skinnyboy_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-09-17"
        version = "1"
        description = "Detects win.skinnyboy."
        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.skinnyboy"
        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 = { 8bf0 d1fe 6a55 ff34f588d40010 ff7508 e8???????? }
            // n = 6, score = 100
            //   8bf0                 | mov                 esi, eax
            //   d1fe                 | sar                 esi, 1
            //   6a55                 | push                0x55
            //   ff34f588d40010       | push                dword ptr [esi*8 + 0x1000d488]
            //   ff7508               | push                dword ptr [ebp + 8]
            //   e8????????           |                     

        $sequence_1 = { ffd6 8b03 85c0 7551 8b35???????? 8d85fcf7ffff }
            // n = 6, score = 100
            //   ffd6                 | call                esi
            //   8b03                 | mov                 eax, dword ptr [ebx]
            //   85c0                 | test                eax, eax
            //   7551                 | jne                 0x53
            //   8b35????????         |                     
            //   8d85fcf7ffff         | lea                 eax, [ebp - 0x804]

        $sequence_2 = { 75f9 2bf1 8d043e 50 }
            // n = 4, score = 100
            //   75f9                 | jne                 0xfffffffb
            //   2bf1                 | sub                 esi, ecx
            //   8d043e               | lea                 eax, [esi + edi]
            //   50                   | push                eax

        $sequence_3 = { 83c004 50 e8???????? eb40 }
            // n = 4, score = 100
            //   83c004               | add                 eax, 4
            //   50                   | push                eax
            //   e8????????           |                     
            //   eb40                 | jmp                 0x42

        $sequence_4 = { 8bb5e0feffff 8b85d8feffff 8b3d???????? 85c0 7403 50 ffd7 }
            // n = 7, score = 100
            //   8bb5e0feffff         | mov                 esi, dword ptr [ebp - 0x120]
            //   8b85d8feffff         | mov                 eax, dword ptr [ebp - 0x128]
            //   8b3d????????         |                     
            //   85c0                 | test                eax, eax
            //   7403                 | je                  5
            //   50                   | push                eax
            //   ffd7                 | call                edi

        $sequence_5 = { 50 ffd6 03c0 50 6a08 ff15???????? 50 }
            // n = 7, score = 100
            //   50                   | push                eax
            //   ffd6                 | call                esi
            //   03c0                 | add                 eax, eax
            //   50                   | push                eax
            //   6a08                 | push                8
            //   ff15????????         |                     
            //   50                   | push                eax

        $sequence_6 = { ff15???????? 6a6f 8d85f5feffff 6a00 50 }
            // n = 5, score = 100
            //   ff15????????         |                     
            //   6a6f                 | push                0x6f
            //   8d85f5feffff         | lea                 eax, [ebp - 0x10b]
            //   6a00                 | push                0
            //   50                   | push                eax

        $sequence_7 = { 8bcf 8bc7 83e11f c1f805 c1e106 030c8510110110 eb05 }
            // n = 7, score = 100
            //   8bcf                 | mov                 ecx, edi
            //   8bc7                 | mov                 eax, edi
            //   83e11f               | and                 ecx, 0x1f
            //   c1f805               | sar                 eax, 5
            //   c1e106               | shl                 ecx, 6
            //   030c8510110110       | add                 ecx, dword ptr [eax*4 + 0x10011110]
            //   eb05                 | jmp                 7

        $sequence_8 = { 8bf7 83e61f c1e606 03348510110110 837e0800 7530 }
            // n = 6, score = 100
            //   8bf7                 | mov                 esi, edi
            //   83e61f               | and                 esi, 0x1f
            //   c1e606               | shl                 esi, 6
            //   03348510110110       | add                 esi, dword ptr [eax*4 + 0x10011110]
            //   837e0800             | cmp                 dword ptr [esi + 8], 0
            //   7530                 | jne                 0x32

        $sequence_9 = { c3 8b3d???????? 50 6a00 ffd7 50 ff15???????? }
            // n = 7, score = 100
            //   c3                   | ret                 
            //   8b3d????????         |                     
            //   50                   | push                eax
            //   6a00                 | push                0
            //   ffd7                 | call                edi
            //   50                   | push                eax
            //   ff15????????         |                     

    condition:
        7 of them and filesize < 176128
}