rule win_krdownloader_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-05-04"
        version = "1"
        description = "Detects win.krdownloader."
        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.krdownloader"
        malpedia_rule_date = "20260422"
        malpedia_hash = "a182e35da64e6d71cb55f125c4d4225196523f14"
        malpedia_version = "20260504"
        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 = { 8b0a 2b08 8bc1 99 b904050000 f7f9 }
            // n = 6, score = 200
            //   8b0a                 | mov                 ecx, dword ptr [edx]
            //   2b08                 | sub                 ecx, dword ptr [eax]
            //   8bc1                 | mov                 eax, ecx
            //   99                   | cdq                 
            //   b904050000           | mov                 ecx, 0x504
            //   f7f9                 | idiv                ecx

        $sequence_1 = { 8d95e9fbffff 52 e8???????? 83c40c 8b45fc 2b45f4 50 }
            // n = 7, score = 200
            //   8d95e9fbffff         | lea                 edx, [ebp - 0x417]
            //   52                   | push                edx
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   8b45fc               | mov                 eax, dword ptr [ebp - 4]
            //   2b45f4               | sub                 eax, dword ptr [ebp - 0xc]
            //   50                   | push                eax

        $sequence_2 = { 6840004004 8d45f4 50 68???????? 68???????? }
            // n = 5, score = 200
            //   6840004004           | push                0x4400040
            //   8d45f4               | lea                 eax, [ebp - 0xc]
            //   50                   | push                eax
            //   68????????           |                     
            //   68????????           |                     

        $sequence_3 = { e8???????? 8945ac 8b4dd8 0fbe540de8 52 8b45d4 0fbe4c05e8 }
            // n = 7, score = 200
            //   e8????????           |                     
            //   8945ac               | mov                 dword ptr [ebp - 0x54], eax
            //   8b4dd8               | mov                 ecx, dword ptr [ebp - 0x28]
            //   0fbe540de8           | movsx               edx, byte ptr [ebp + ecx - 0x18]
            //   52                   | push                edx
            //   8b45d4               | mov                 eax, dword ptr [ebp - 0x2c]
            //   0fbe4c05e8           | movsx               ecx, byte ptr [ebp + eax - 0x18]

        $sequence_4 = { 83c408 837d1000 7509 c745f801000000 eb07 }
            // n = 5, score = 200
            //   83c408               | add                 esp, 8
            //   837d1000             | cmp                 dword ptr [ebp + 0x10], 0
            //   7509                 | jne                 0xb
            //   c745f801000000       | mov                 dword ptr [ebp - 8], 1
            //   eb07                 | jmp                 9

        $sequence_5 = { 6a00 6840004004 8d45f4 50 68???????? 68???????? }
            // n = 6, score = 200
            //   6a00                 | push                0
            //   6840004004           | push                0x4400040
            //   8d45f4               | lea                 eax, [ebp - 0xc]
            //   50                   | push                eax
            //   68????????           |                     
            //   68????????           |                     

        $sequence_6 = { 837dec00 0f850a010000 8b4df8 894dfc 837dfc00 0f84fa000000 }
            // n = 6, score = 200
            //   837dec00             | cmp                 dword ptr [ebp - 0x14], 0
            //   0f850a010000         | jne                 0x110
            //   8b4df8               | mov                 ecx, dword ptr [ebp - 8]
            //   894dfc               | mov                 dword ptr [ebp - 4], ecx
            //   837dfc00             | cmp                 dword ptr [ebp - 4], 0
            //   0f84fa000000         | je                  0x100

        $sequence_7 = { 894df8 c745fc00000000 c745f400000000 eb0c 8b45f8 8b4df4 034804 }
            // n = 7, score = 200
            //   894df8               | mov                 dword ptr [ebp - 8], ecx
            //   c745fc00000000       | mov                 dword ptr [ebp - 4], 0
            //   c745f400000000       | mov                 dword ptr [ebp - 0xc], 0
            //   eb0c                 | jmp                 0xe
            //   8b45f8               | mov                 eax, dword ptr [ebp - 8]
            //   8b4df4               | mov                 ecx, dword ptr [ebp - 0xc]
            //   034804               | add                 ecx, dword ptr [eax + 4]

        $sequence_8 = { 50 680000a000 8b4dec 51 6a00 }
            // n = 5, score = 200
            //   50                   | push                eax
            //   680000a000           | push                0xa00000
            //   8b4dec               | mov                 ecx, dword ptr [ebp - 0x14]
            //   51                   | push                ecx
            //   6a00                 | push                0

        $sequence_9 = { c745bc00000000 c745e002000000 c745e8983a0000 8b45e8 50 }
            // n = 5, score = 200
            //   c745bc00000000       | mov                 dword ptr [ebp - 0x44], 0
            //   c745e002000000       | mov                 dword ptr [ebp - 0x20], 2
            //   c745e8983a0000       | mov                 dword ptr [ebp - 0x18], 0x3a98
            //   8b45e8               | mov                 eax, dword ptr [ebp - 0x18]
            //   50                   | push                eax

    condition:
        7 of them and filesize < 352256
}