rule win_nautilus_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-11-21"
        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 = "20221118"
        malpedia_hash = "e0702e2e6d1d00da65c8a29a4ebacd0a4c59e1af"
        malpedia_version = "20221125"
        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 = { 4889442440 e8???????? 4863d8 85c0 786c 4c8d442448 488d5580 }
            // n = 7, score = 100
            //   4889442440           | lea                 edx, [ecx + 1]
            //   e8????????           |                     
            //   4863d8               | inc                 ebp
            //   85c0                 | xor                 ecx, ecx
            //   786c                 | inc                 ebp
            //   4c8d442448           | xor                 eax, eax
            //   488d5580             | inc                 ecx

        $sequence_1 = { c4e2e1a92d???????? c4e2e1a92d???????? c4e2e1a92d???????? c5fb59e3 c5db59d5 c5f3592d???????? c5d35cd2 }
            // n = 7, score = 100
            //   c4e2e1a92d????????     |     
            //   c4e2e1a92d????????     |     
            //   c4e2e1a92d????????     |     
            //   c5fb59e3             | mov                 ebx, 3
            //   c5db59d5             | dec                 eax
            //   c5f3592d????????     |                     
            //   c5d35cd2             | lea                 ecx, [ebx + 0x520]

        $sequence_2 = { e8???????? eb03 4533e4 488bcb e8???????? 488b5d5f eb43 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   eb03                 | cmp                 dword ptr [ebx], 6
            //   4533e4               | jle                 0x5d7
            //   488bcb               | cmp                 dword ptr [ebx], 7
            //   e8????????           |                     
            //   488b5d5f             | je                  0x55e
            //   eb43                 | cmp                 dword ptr [ebx], 3

        $sequence_3 = { ff16 4183c8ff 488bcb 418d50ff e8???????? 488bcb 85c0 }
            // n = 7, score = 100
            //   ff16                 | lea                 esi, [ebx + 0x88]
            //   4183c8ff             | dec                 eax
            //   488bcb               | lea                 edx, [ebp - 0x29]
            //   418d50ff             | dec                 ecx
            //   e8????????           |                     
            //   488bcb               | mov                 ecx, esi
            //   85c0                 | test                eax, eax

        $sequence_4 = { 8bf0 85c0 7553 488d5c2420 483bfd 7411 488bd5 }
            // n = 7, score = 100
            //   8bf0                 | dec                 eax
            //   85c0                 | test                eax, eax
            //   7553                 | je                  0x4ee
            //   488d5c2420           | dec                 eax
            //   483bfd               | mov                 ecx, dword ptr [ecx + 8]
            //   7411                 | dec                 eax
            //   488bd5               | jmp                 dword ptr [eax + 0x10]

        $sequence_5 = { e8???????? 85c0 0f84a8010000 488d55e0 488bce e8???????? 85c0 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   85c0                 | cmp                 byte ptr [edx], 0
            //   0f84a8010000         | jne                 0xe1
            //   488d55e0             | jge                 0xcc
            //   488bce               | or                  ebx, 0xffffffff
            //   e8????????           |                     
            //   85c0                 | jmp                 0xfc

        $sequence_6 = { eb07 ffc3 488bce 8bd3 e8???????? 83780800 75ee }
            // n = 7, score = 100
            //   eb07                 | arpl                ax, cx
            //   ffc3                 | dec                 ebp
            //   488bce               | mov                 eax, edx
            //   8bd3                 | inc                 ecx
            //   e8????????           |                     
            //   83780800             | mov                 dl, dl
            //   75ee                 | dec                 ecx

        $sequence_7 = { 8b4308 eb03 83c8ff 488d5310 448bc0 488bcf e8???????? }
            // n = 7, score = 100
            //   8b4308               | dec                 eax
            //   eb03                 | sub                 esp, 0x20
            //   83c8ff               | dec                 eax
            //   488d5310             | mov                 eax, dword ptr [ecx]
            //   448bc0               | dec                 eax
            //   488bcf               | mov                 ebx, ecx
            //   e8????????           |                     

        $sequence_8 = { e8???????? 4c8b4708 488d4db0 488bd3 e8???????? 8bd8 85c0 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   4c8b4708             | dec                 eax
            //   488d4db0             | sub                 ecx, 4
            //   488bd3               | dec                 eax
            //   e8????????           |                     
            //   8bd8                 | dec                 esi
            //   85c0                 | jns                 0x27c

        $sequence_9 = { 420fb6843090000000 eb08 418a12 e8???????? 3bc6 0f8498000000 85c0 }
            // n = 7, score = 100
            //   420fb6843090000000     | inc    ecx
            //   eb08                 | movzx               eax, word ptr [esp + ecx*2 + 0x58]
            //   418a12               | inc                 ecx
            //   e8????????           |                     
            //   3bc6                 | movzx               eax, word ptr [esp + ecx*2 + 0x56]
            //   0f8498000000         | dec                 eax
            //   85c0                 | add                 eax, edx

    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_*)) 
}