rule win_royal_dns_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        version = "1"
        description = "Detects win.royal_dns."
        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.royal_dns"
        malpedia_rule_date = "20220405"
        malpedia_hash = "ecd38294bd47d5589be5cd5490dc8bb4804afc2a"
        malpedia_version = "20220411"
        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 = { 80e101 0ad9 32c0 68ff000000 02db 24f5 }
            // n = 6, score = 100
            //   80e101               | and                 cl, 1
            //   0ad9                 | or                  bl, cl
            //   32c0                 | xor                 al, al
            //   68ff000000           | push                0xff
            //   02db                 | add                 bl, bl
            //   24f5                 | and                 al, 0xf5

        $sequence_1 = { fe06 8a1401 881437 47 eb0a 03f7 }
            // n = 6, score = 100
            //   fe06                 | inc                 byte ptr [esi]
            //   8a1401               | mov                 dl, byte ptr [ecx + eax]
            //   881437               | mov                 byte ptr [edi + esi], dl
            //   47                   | inc                 edi
            //   eb0a                 | jmp                 0xc
            //   03f7                 | add                 esi, edi

        $sequence_2 = { 83ee02 7417 4e 7520 8bc1 c1e810 }
            // n = 6, score = 100
            //   83ee02               | sub                 esi, 2
            //   7417                 | je                  0x19
            //   4e                   | dec                 esi
            //   7520                 | jne                 0x22
            //   8bc1                 | mov                 eax, ecx
            //   c1e810               | shr                 eax, 0x10

        $sequence_3 = { 4a 759a 8b55fc 85ff 7468 0fb606 c1e802 }
            // n = 7, score = 100
            //   4a                   | dec                 edx
            //   759a                 | jne                 0xffffff9c
            //   8b55fc               | mov                 edx, dword ptr [ebp - 4]
            //   85ff                 | test                edi, edi
            //   7468                 | je                  0x6a
            //   0fb606               | movzx               eax, byte ptr [esi]
            //   c1e802               | shr                 eax, 2

        $sequence_4 = { 83ec20 a1???????? 33c5 8945fc 8b4508 33c9 8d55e0 }
            // n = 7, score = 100
            //   83ec20               | sub                 esp, 0x20
            //   a1????????           |                     
            //   33c5                 | xor                 eax, ebp
            //   8945fc               | mov                 dword ptr [ebp - 4], eax
            //   8b4508               | mov                 eax, dword ptr [ebp + 8]
            //   33c9                 | xor                 ecx, ecx
            //   8d55e0               | lea                 edx, dword ptr [ebp - 0x20]

        $sequence_5 = { 8a08 80e104 0fb6c9 4e 33d2 f7d9 1bc9 }
            // n = 7, score = 100
            //   8a08                 | mov                 cl, byte ptr [eax]
            //   80e104               | and                 cl, 4
            //   0fb6c9               | movzx               ecx, cl
            //   4e                   | dec                 esi
            //   33d2                 | xor                 edx, edx
            //   f7d9                 | neg                 ecx
            //   1bc9                 | sbb                 ecx, ecx

        $sequence_6 = { 8b0f 6683790600 0f86e7000000 680a010000 }
            // n = 4, score = 100
            //   8b0f                 | mov                 ecx, dword ptr [edi]
            //   6683790600           | cmp                 word ptr [ecx + 6], 0
            //   0f86e7000000         | jbe                 0xed
            //   680a010000           | push                0x10a

        $sequence_7 = { 8985b4fcffff 8bf8 6a08 e8???????? }
            // n = 4, score = 100
            //   8985b4fcffff         | mov                 dword ptr [ebp - 0x34c], eax
            //   8bf8                 | mov                 edi, eax
            //   6a08                 | push                8
            //   e8????????           |                     

        $sequence_8 = { 83c40c 68fd000000 8995d0faffff 8d95d7faffff 6a00 }
            // n = 5, score = 100
            //   83c40c               | add                 esp, 0xc
            //   68fd000000           | push                0xfd
            //   8995d0faffff         | mov                 dword ptr [ebp - 0x530], edx
            //   8d95d7faffff         | lea                 edx, dword ptr [ebp - 0x529]
            //   6a00                 | push                0

        $sequence_9 = { c0e205 0ac2 8a55f7 885dec }
            // n = 4, score = 100
            //   c0e205               | shl                 dl, 5
            //   0ac2                 | or                  al, dl
            //   8a55f7               | mov                 dl, byte ptr [ebp - 9]
            //   885dec               | mov                 byte ptr [ebp - 0x14], bl

    condition:
        7 of them and filesize < 204800
}

import "pe"

rule win_royal_dns_w0 {
    meta:
        author = "Florian Roth"
        description = "Detects malware from APT 15 report by NCC Group"
        reference = "https://goo.gl/HZ5XMN"
        date = "2018-03-10"
        hash = "bc937f6e958b339f6925023bc2af375d669084e9551fd3753e501ef26e36b39d"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.royal_dns"
        malpedia_version = "20180312"
        malpedia_license = "CC BY-NC-SA 4.0"
        malpedia_sharing = "TLP:WHITE"
    strings:
        $x1 = "del c:\\windows\\temp\\r.exe /f /q" fullword ascii
        $x2 = "%s\\r.exe" fullword ascii

        $s1 = "rights.dll" fullword ascii
        $s2 = "\"%s\">>\"%s\"\\s.txt" fullword ascii
        $s3 = "Nwsapagent" fullword ascii
        $s4 = "%s\\r.bat" fullword ascii
        $s5 = "%s\\s.txt" fullword ascii
        $s6 = "runexe" fullword ascii
    condition:
        1 of ($x*) or 2 of them
}

rule win_royal_dns_w1 {
    meta:
        author = "David Cannings"
        description = "DLL implant, originally rights.dll and runs as a service"
        hash = "bc937f6e958b339f6925023bc2af375d669084e9551fd3753e501ef26e36b39d"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.royal_dns"
        malpedia_version = "20180312"
        malpedia_license = "CC BY-NC-SA 4.0"
        malpedia_sharing = "TLP:WHITE"
    strings:
        /*
        56                push    esi
        B8 A7 C6 67 4E    mov     eax, 4E67C6A7h
        83 C1 02          add     ecx, 2
        BA 04 00 00 00    mov     edx, 4
        57                push    edi
        90                nop
        */
        // JSHash implementation (Justin Sobel's hash algorithm)
        $opcodes_jshash = { B8 A7 C6 67 4E 83 C1 02 BA 04 00 00 00 57 90 }

        /*
        0F B6 1C 03       movzx   ebx, byte ptr [ebx+eax]
        8B 55 08          mov     edx, [ebp+arg_0]
        30 1C 17          xor     [edi+edx], bl
        47                inc     edi
        3B 7D 0C          cmp     edi, [ebp+arg_4]
        72 A4             jb      short loc_10003F31
        */
        // Encode loop, used to "encrypt" data before DNS request
        $opcodes_encode = { 0F B6 1C 03 8B 55 08 30 1C 17 47 3B 7D 0C }

        /*
        68 88 13 00 00    push    5000 # Also seen 3000, included below
        FF D6             call    esi ; Sleep
        4F                dec     edi
        75 F6             jnz     short loc_10001554
        */
        // Sleep loop
        $opcodes_sleep_loop = { 68 (88|B8) (13|0B) 00 00 FF D6 4F 75 F6 }

        // Generic strings
        $ = "Nwsapagent" fullword
        $ = "\"%s\">>\"%s\"\\s.txt"
        $ = "myWObject" fullword
        $ = "del c:\\windows\\temp\\r.exe /f /q"
        $ = "del c:\\windows\\temp\\r.ini /f /q"

    condition:
        3 of them
}