rule win_kerrdown_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        version = "1"
        description = "Detects win.kerrdown."
        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.kerrdown"
        malpedia_rule_date = "20230124"
        malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686"
        malpedia_version = "20230125"
        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 = { 1e f2cd3a bdbe33f88e 0a627a }
            // n = 4, score = 200
            //   1e                   | push                ds
            //   f2cd3a               | int                 0x3a
            //   bdbe33f88e           | mov                 ebp, 0x8ef833be
            //   0a627a               | or                  ah, byte ptr [edx + 0x7a]

        $sequence_1 = { c64405e800 40 83f804 7cef 33db 0f1f4000 }
            // n = 6, score = 200
            //   c64405e800           | mov                 byte ptr [ebp + eax - 0x18], 0
            //   40                   | inc                 eax
            //   83f804               | cmp                 eax, 4
            //   7cef                 | jl                  0xfffffff1
            //   33db                 | xor                 ebx, ebx
            //   0f1f4000             | nop                 dword ptr [eax]

        $sequence_2 = { de05???????? 7f75 7217 a4 7d15 6bcdac 73d0 }
            // n = 7, score = 200
            //   de05????????         |                     
            //   7f75                 | jg                  0x77
            //   7217                 | jb                  0x19
            //   a4                   | movsb               byte ptr es:[edi], byte ptr [esi]
            //   7d15                 | jge                 0x17
            //   6bcdac               | imul                ecx, ebp, -0x54
            //   73d0                 | jae                 0xffffffd2

        $sequence_3 = { 80fb3d 0f84ad000000 0fb6c3 50 e8???????? 83c404 85c0 }
            // n = 7, score = 200
            //   80fb3d               | cmp                 bl, 0x3d
            //   0f84ad000000         | je                  0xb3
            //   0fb6c3               | movzx               eax, bl
            //   50                   | push                eax
            //   e8????????           |                     
            //   83c404               | add                 esp, 4
            //   85c0                 | test                eax, eax

        $sequence_4 = { 7d2a 8afe 3adb e07c }
            // n = 4, score = 200
            //   7d2a                 | jge                 0x2c
            //   8afe                 | mov                 bh, dh
            //   3adb                 | cmp                 bl, bl
            //   e07c                 | loopne              0x7e

        $sequence_5 = { 6f d80b 8be5 59 dab2aa46c72b 308711e6952c }
            // n = 6, score = 200
            //   6f                   | outsd               dx, dword ptr [esi]
            //   d80b                 | fmul                dword ptr [ebx]
            //   8be5                 | mov                 esp, ebp
            //   59                   | pop                 ecx
            //   dab2aa46c72b         | fidiv               dword ptr [edx + 0x2bc746aa]
            //   308711e6952c         | xor                 byte ptr [edi + 0x2c95e611], al

        $sequence_6 = { 8ac4 80e203 c0e004 02d1 8855e4 8a55ea }
            // n = 6, score = 200
            //   8ac4                 | mov                 al, ah
            //   80e203               | and                 dl, 3
            //   c0e004               | shl                 al, 4
            //   02d1                 | add                 dl, cl
            //   8855e4               | mov                 byte ptr [ebp - 0x1c], dl
            //   8a55ea               | mov                 dl, byte ptr [ebp - 0x16]

        $sequence_7 = { 75be ddd8 db2d???????? b802000000 833d????????00 0f85400a0000 }
            // n = 6, score = 200
            //   75be                 | jne                 0xffffffc0
            //   ddd8                 | fstp                st(0)
            //   db2d????????         |                     
            //   b802000000           | mov                 eax, 2
            //   833d????????00       |                     
            //   0f85400a0000         | jne                 0xa46

        $sequence_8 = { 8bd3 2bd6 8a0e 8d7601 884c32ff 84c9 75f3 }
            // n = 7, score = 200
            //   8bd3                 | mov                 edx, ebx
            //   2bd6                 | sub                 edx, esi
            //   8a0e                 | mov                 cl, byte ptr [esi]
            //   8d7601               | lea                 esi, [esi + 1]
            //   884c32ff             | mov                 byte ptr [edx + esi - 1], cl
            //   84c9                 | test                cl, cl
            //   75f3                 | jne                 0xfffffff5

        $sequence_9 = { f1 f6a2a19e0188 0569e1e9cf bdea322709 1d7fd77368 6c }
            // n = 6, score = 200
            //   f1                   | int1                
            //   f6a2a19e0188         | mul                 byte ptr [edx - 0x77fe615f]
            //   0569e1e9cf           | add                 eax, 0xcfe9e169
            //   bdea322709           | mov                 ebp, 0x92732ea
            //   1d7fd77368           | sbb                 eax, 0x6873d77f
            //   6c                   | insb                byte ptr es:[edi], dx

    condition:
        7 of them and filesize < 278528
}