rule win_nautilus_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2021-06-10"
        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 = "20210604"
        malpedia_hash = "be09d5d71e77373c0f538068be31a2ad4c69cfbd"
        malpedia_version = "20210616"
        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 = { 7606 4183c9ff eb2d 498b12 478d0c89 0fbe02 458d49e8 }
            // n = 7, score = 100
            //   7606                 | dec                 ecx
            //   4183c9ff             | mov                 ecx, esi
            //   eb2d                 | movzx               edx, byte ptr [esi + eax]
            //   498b12               | dec                 ecx
            //   478d0c89             | mov                 ecx, esi
            //   0fbe02               | movzx               edx, byte ptr [esi + eax]
            //   458d49e8             | inc                 esp

        $sequence_1 = { 750a b880b0ffff e9???????? 488b4d77 bb01000000 8bd3 e8???????? }
            // n = 7, score = 100
            //   750a                 | cmp                 edx, eax
            //   b880b0ffff           | je                  0x495
            //   e9????????           |                     
            //   488b4d77             | cmp                 byte ptr [edx], cl
            //   bb01000000           | jne                 0x495
            //   8bd3                 | dec                 eax
            //   e8????????           |                     

        $sequence_2 = { eb02 8ada 301f ffc1 83f910 1bc0 48ffc7 }
            // n = 7, score = 100
            //   eb02                 | jne                 0x701
            //   8ada                 | inc                 ecx
            //   301f                 | movzx               eax, byte ptr [edx + 1]
            //   ffc1                 | movzx               ecx, byte ptr [eax + esi + 0x870d0]
            //   83f910               | inc                 ebp
            //   1bc0                 | movzx               eax, al
            //   48ffc7               | sub                 eax, 2

        $sequence_3 = { e8???????? 488d542420 41b808000000 488bcb e8???????? 8a4308 8807 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   488d542420           | arpl                ax, dx
            //   41b808000000         | mov                 dword ptr [ebx + 0x14], eax
            //   488bcb               | dec                 eax
            //   e8????????           |                     
            //   8a4308               | shl                 edx, 3
            //   8807                 | jne                 0x93b

        $sequence_4 = { c7010c000000 894108 488bcb e8???????? 488bcf e8???????? 488b9c24d0000000 }
            // n = 7, score = 100
            //   c7010c000000         | jne                 0x5a1
            //   894108               | inc                 ebp
            //   488bcb               | movzx               eax, byte ptr [edx + 1]
            //   e8????????           |                     
            //   488bcf               | inc                 ecx
            //   e8????????           |                     
            //   488b9c24d0000000     | movzx               eax, byte ptr [eax + ebx + 0x90]

        $sequence_5 = { 803b20 74f8 488d0d48c90300 41b803000000 488bd3 e8???????? 85c0 }
            // n = 7, score = 100
            //   803b20               | jg                  0xb3d
            //   74f8                 | dec                 ecx
            //   488d0d48c90300       | mov                 esi, ecx
            //   41b803000000         | dec                 ebp
            //   488bd3               | mov                 esp, eax
            //   e8????????           |                     
            //   85c0                 | dec                 eax

        $sequence_6 = { c744242020000000 e8???????? 44396d60 0f87e9000000 bafeffff7f 33c9 e8???????? }
            // n = 7, score = 100
            //   c744242020000000     | dec                 eax
            //   e8????????           |                     
            //   44396d60             | mov                 ecx, eax
            //   0f87e9000000         | inc                 esp
            //   bafeffff7f           | movzx               esp, al
            //   33c9                 | dec                 eax
            //   e8????????           |                     

        $sequence_7 = { 83ffe4 0f8d25010000 4885ed 0f851c010000 81ffcefbffff 7d1a 4885f6 }
            // n = 7, score = 100
            //   83ffe4               | dec                 esp
            //   0f8d25010000         | mov                 eax, eax
            //   4885ed               | dec                 eax
            //   0f851c010000         | mov                 dword ptr [esp + 0x40], eax
            //   81ffcefbffff         | test                eax, eax
            //   7d1a                 | jne                 0x4da
            //   4885f6               | movzx               ecx, byte ptr [ebx]

        $sequence_8 = { e8???????? 85c0 7404 33c0 eb6c 8b442478 85c0 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   85c0                 | jmp                 0x388
            //   7404                 | inc                 ecx
            //   33c0                 | mov                 eax, dword ptr [eax + 0xfa50]
            //   eb6c                 | inc                 ecx
            //   8b442478             | mov                 edx, dword ptr [eax + 0x444]
            //   85c0                 | inc                 esp

        $sequence_9 = { 488b4e10 488b5158 8b4a18 c645f900 894df4 488b4618 488945e8 }
            // n = 7, score = 100
            //   488b4e10             | dec                 eax
            //   488b5158             | cmp                 ebx, 0x40
            //   8b4a18               | jb                  0x5e7
            //   c645f900             | dec                 eax
            //   894df4               | mov                 ebp, ebx
            //   488b4618             | dec                 eax
            //   488945e8             | shr                 ebp, 6

    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_*)) 
}