rule win_nautilus_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-09-17"
        version = "1"
        description = "Detects win.nautilus."
        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.nautilus"
        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 = { 83e803 741c 83e802 7417 83f805 0f8596000000 410fb602 }
            // n = 7, score = 100
            //   83e803               | test                eax, eax
            //   741c                 | dec                 eax
            //   83e802               | mov                 dword ptr [ebp - 0x38], edi
            //   7417                 | dec                 eax
            //   83f805               | mov                 dword ptr [ebp - 0x30], edi
            //   0f8596000000         | dec                 eax
            //   410fb602             | mov                 ecx, dword ptr [ebx + 0x18]

        $sequence_1 = { e8???????? 8bd8 85c0 755b 488d4558 488d542438 488d4c2420 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   8bd8                 | inc                 ecx
            //   85c0                 | sub                 eax, ebp
            //   755b                 | sub                 edx, esi
            //   488d4558             | dec                 eax
            //   488d542438           | lea                 edx, [edx + 4]
            //   488d4c2420           | dec                 eax

        $sequence_2 = { e9???????? 488b3b 396f08 0f84011a0000 488b07 8b5320 0fb608 }
            // n = 7, score = 100
            //   e9????????           |                     
            //   488b3b               | mov                 edx, edi
            //   396f08               | dec                 eax
            //   0f84011a0000         | lea                 edi, [esi + 8]
            //   488b07               | jmp                 0x1280
            //   8b5320               | dec                 eax
            //   0fb608               | lea                 edx, [ebp - 0x48]

        $sequence_3 = { 488b7c2448 4883c420 415e c3 488bc8 488bd5 e8???????? }
            // n = 7, score = 100
            //   488b7c2448           | inc                 ecx
            //   4883c420             | mov                 ch, 1
            //   415e                 | inc                 ecx
            //   c3                   | cmp                 edi, 1
            //   488bc8               | jne                 0xd8a
            //   488bd5               | dec                 ecx
            //   e8????????           |                     

        $sequence_4 = { 75be 48ffc2 493bd2 7507 b8fdffffff ebb7 0fb602 }
            // n = 7, score = 100
            //   75be                 | mov                 ecx, esi
            //   48ffc2               | lea                 edi, [eax + 0x12]
            //   493bd2               | dec                 eax
            //   7507                 | mov                 dword ptr [ebx + 0x30], eax
            //   b8fdffffff           | dec                 eax
            //   ebb7                 | mov                 dword ptr [ebx + 0x38], eax
            //   0fb602               | mov                 dword ptr [ebx + 0x48], esi

        $sequence_5 = { 783e eb03 488bee 488b442440 48ffc0 4889442440 488d142b }
            // n = 7, score = 100
            //   783e                 | dec                 eax
            //   eb03                 | lea                 eax, [esp + 0x38]
            //   488bee               | dec                 eax
            //   488b442440           | lea                 edx, [esp + 0x60]
            //   48ffc0               | dec                 ebp
            //   4889442440           | mov                 ebp, eax
            //   488d142b             | dec                 esp

        $sequence_6 = { d3f8 498bcf 412006 837c244000 c60433bc 750d 4d8bc6 }
            // n = 7, score = 100
            //   d3f8                 | dec                 eax
            //   498bcf               | inc                 edi
            //   412006               | dec                 eax
            //   837c244000           | lea                 edx, [ebx + 0x50]
            //   c60433bc             | inc                 ecx
            //   750d                 | mov                 ecx, 0x18
            //   4d8bc6               | dec                 esp

        $sequence_7 = { 488bc8 e8???????? 891f 33c0 488b8c2460010000 4833cc }
            // n = 6, score = 100
            //   488bc8               | shl                 ecx, 5
            //   e8????????           |                     
            //   891f                 | inc                 edx
            //   33c0                 | movups              xmm0, xmmword ptr [ecx + eax + 0x10]
            //   488b8c2460010000     | movdqu              xmmword ptr [edi], xmm0
            //   4833cc               | inc                 ecx

        $sequence_8 = { e9???????? c74424200e000000 e9???????? 8bc7 41b800010000 41bd13000000 c1e817 }
            // n = 7, score = 100
            //   e9????????           |                     
            //   c74424200e000000     | xor                 edi, dword ptr [ebp + eax*4 + 0x94ce0]
            //   e9????????           |                     
            //   8bc7                 | inc                 ecx
            //   41b800010000         | movzx               eax, cl
            //   41bd13000000         | inc                 ecx
            //   c1e817               | xor                 edi, dword ptr [ebp + eax*4 + 0x940e0]

        $sequence_9 = { 7512 8a4a01 80f9a0 7230 4122c9 413ac9 752d }
            // n = 7, score = 100
            //   7512                 | dec                 eax
            //   8a4a01               | test                ecx, ecx
            //   80f9a0               | je                  0x335
            //   7230                 | dec                 eax
            //   4122c9               | test                edx, edx
            //   413ac9               | je                  0x335
            //   752d                 | dec                 eax

    condition:
        7 of them and filesize < 1302528
}

rule win_nautilus_w0 {
    meta:
        description = "Rule for detection of Nautilus based on assembly code for a modified RC4 loop"
        author = "NCSC UK"
        hash = "a415ab193f6cd832a0de4fcc48d5f53d6f0b06d5e13b3c359878c6c31f3e7ec3"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.nautilus"
        malpedia_version = "20180226"
        malpedia_license = "CC BY-NC-SA 4.0"
        malpedia_sharing = "TLP:WHITE"
    strings:
        $rc4_loop = {42 0F B6 14 04 41 FF C0 03 D7 0F B6 CA 8A 14 0C 43 32 14 13 41 88 12 49 FF C2
        49 FF C9}
        $rc4_key = {31 42 31 34 34 30 44 39 30 46 43 39 42 43 42 34 36 41 39 41 43 39 36 34 33 38
        46 45 45 41 38 42}
        $string_0 = "nautilus-service.dll" ascii
        $string_1 = "oxygen.dll" ascii
        $string_2 = "config_listen.system" ascii
        $string_3 = "ctx.system" ascii
        $string_4 = "3FDA3998-BEF5-426D-82D8-1A71F29ADDC3" ascii
        $string_5 = "C:\\ProgramData\\Microsoft\\Windows\\Caches\\{%s}.2.ver0x0000000000000001.db"
    condition:
        ($rc4_loop and $rc4_key) or (all of ($string_*)) 
}