rule win_nullmixer_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-05-04"
        version = "1"
        description = "Detects win.nullmixer."
        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.nullmixer"
        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 = { 8b04bb 8b0486 890424 e8???????? 8b4de0 8904b9 83c701 }
            // n = 7, score = 100
            //   8b04bb               | mov                 eax, dword ptr [ebx + edi*4]
            //   8b0486               | mov                 eax, dword ptr [esi + eax*4]
            //   890424               | mov                 dword ptr [esp], eax
            //   e8????????           |                     
            //   8b4de0               | mov                 ecx, dword ptr [ebp - 0x20]
            //   8904b9               | mov                 dword ptr [ecx + edi*4], eax
            //   83c701               | add                 edi, 1

        $sequence_1 = { 0f85ac020000 807dc000 740a f75dc8 8355cc00 f75dcc 8b5d20 }
            // n = 7, score = 100
            //   0f85ac020000         | jne                 0x2b2
            //   807dc000             | cmp                 byte ptr [ebp - 0x40], 0
            //   740a                 | je                  0xc
            //   f75dc8               | neg                 dword ptr [ebp - 0x38]
            //   8355cc00             | adc                 dword ptr [ebp - 0x34], 0
            //   f75dcc               | neg                 dword ptr [ebp - 0x34]
            //   8b5d20               | mov                 ebx, dword ptr [ebp + 0x20]

        $sequence_2 = { 55 89e5 56 53 51 81ecbc020000 e8???????? }
            // n = 7, score = 100
            //   55                   | push                ebp
            //   89e5                 | mov                 ebp, esp
            //   56                   | push                esi
            //   53                   | push                ebx
            //   51                   | push                ecx
            //   81ecbc020000         | sub                 esp, 0x2bc
            //   e8????????           |                     

        $sequence_3 = { 8b45cc 31d2 8b480c 394808 0f8207fdffff 89c1 8b00 }
            // n = 7, score = 100
            //   8b45cc               | mov                 eax, dword ptr [ebp - 0x34]
            //   31d2                 | xor                 edx, edx
            //   8b480c               | mov                 ecx, dword ptr [eax + 0xc]
            //   394808               | cmp                 dword ptr [eax + 8], ecx
            //   0f8207fdffff         | jb                  0xfffffd0d
            //   89c1                 | mov                 ecx, eax
            //   8b00                 | mov                 eax, dword ptr [eax]

        $sequence_4 = { 0f9fc2 01c7 0855bb 8345cc01 8b4108 3b410c 0f8301030000 }
            // n = 7, score = 100
            //   0f9fc2               | setg                dl
            //   01c7                 | add                 edi, eax
            //   0855bb               | or                  byte ptr [ebp - 0x45], dl
            //   8345cc01             | add                 dword ptr [ebp - 0x34], 1
            //   8b4108               | mov                 eax, dword ptr [ecx + 8]
            //   3b410c               | cmp                 eax, dword ptr [ecx + 0xc]
            //   0f8301030000         | jae                 0x307

        $sequence_5 = { 83c701 39f9 75f0 89bc24ac000000 896c2440 8b6c2444 90 }
            // n = 7, score = 100
            //   83c701               | add                 edi, 1
            //   39f9                 | cmp                 ecx, edi
            //   75f0                 | jne                 0xfffffff2
            //   89bc24ac000000       | mov                 dword ptr [esp + 0xac], edi
            //   896c2440             | mov                 dword ptr [esp + 0x40], ebp
            //   8b6c2444             | mov                 ebp, dword ptr [esp + 0x44]
            //   90                   | nop                 

        $sequence_6 = { 0fb645b2 8b4d08 8845b1 8b4108 3b410c 72ac 8b01 }
            // n = 7, score = 100
            //   0fb645b2             | movzx               eax, byte ptr [ebp - 0x4e]
            //   8b4d08               | mov                 ecx, dword ptr [ebp + 8]
            //   8845b1               | mov                 byte ptr [ebp - 0x4f], al
            //   8b4108               | mov                 eax, dword ptr [ecx + 8]
            //   3b410c               | cmp                 eax, dword ptr [ecx + 0xc]
            //   72ac                 | jb                  0xffffffae
            //   8b01                 | mov                 eax, dword ptr [ecx]

        $sequence_7 = { 8b4108 3b410c 0f8384000000 0fb700 31d2 6683f8ff 0f856ffcffff }
            // n = 7, score = 100
            //   8b4108               | mov                 eax, dword ptr [ecx + 8]
            //   3b410c               | cmp                 eax, dword ptr [ecx + 0xc]
            //   0f8384000000         | jae                 0x8a
            //   0fb700               | movzx               eax, word ptr [eax]
            //   31d2                 | xor                 edx, edx
            //   6683f8ff             | cmp                 ax, -1
            //   0f856ffcffff         | jne                 0xfffffc75

        $sequence_8 = { 83ec2c 8b44244c 8b542440 8b742454 8b5c2450 0fbe4c2444 8b7c2448 }
            // n = 7, score = 100
            //   83ec2c               | sub                 esp, 0x2c
            //   8b44244c             | mov                 eax, dword ptr [esp + 0x4c]
            //   8b542440             | mov                 edx, dword ptr [esp + 0x40]
            //   8b742454             | mov                 esi, dword ptr [esp + 0x54]
            //   8b5c2450             | mov                 ebx, dword ptr [esp + 0x50]
            //   0fbe4c2444           | movsx               ecx, byte ptr [esp + 0x44]
            //   8b7c2448             | mov                 edi, dword ptr [esp + 0x48]

        $sequence_9 = { 8b4d14 89c7 8b450c c7470400000000 8b00 c707???????? c7470800000000 }
            // n = 7, score = 100
            //   8b4d14               | mov                 ecx, dword ptr [ebp + 0x14]
            //   89c7                 | mov                 edi, eax
            //   8b450c               | mov                 eax, dword ptr [ebp + 0xc]
            //   c7470400000000       | mov                 dword ptr [edi + 4], 0
            //   8b00                 | mov                 eax, dword ptr [eax]
            //   c707????????         |                     
            //   c7470800000000       | mov                 dword ptr [edi + 8], 0

    condition:
        7 of them and filesize < 2351104
}