rule win_mailto_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        version = "1"
        description = "Detects win.mailto."
        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.mailto"
        malpedia_rule_date = "20230705"
        malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41"
        malpedia_version = "20230715"
        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 = { e8???????? ff742420 e8???????? 56 e8???????? 55 e8???????? }
            // n = 7, score = 400
            //   e8????????           |                     
            //   ff742420             | push                dword ptr [esp + 0x20]
            //   e8????????           |                     
            //   56                   | push                esi
            //   e8????????           |                     
            //   55                   | push                ebp
            //   e8????????           |                     

        $sequence_1 = { 46 8bc4 89742428 0f10442420 8b11 51 }
            // n = 6, score = 400
            //   46                   | inc                 esi
            //   8bc4                 | mov                 eax, esp
            //   89742428             | mov                 dword ptr [esp + 0x28], esi
            //   0f10442420           | movups              xmm0, xmmword ptr [esp + 0x20]
            //   8b11                 | mov                 edx, dword ptr [ecx]
            //   51                   | push                ecx

        $sequence_2 = { 8d4810 0fb744240c 50 ff742414 8b01 56 }
            // n = 6, score = 400
            //   8d4810               | lea                 ecx, [eax + 0x10]
            //   0fb744240c           | movzx               eax, word ptr [esp + 0xc]
            //   50                   | push                eax
            //   ff742414             | push                dword ptr [esp + 0x14]
            //   8b01                 | mov                 eax, dword ptr [ecx]
            //   56                   | push                esi

        $sequence_3 = { 57 e8???????? 83c408 85c0 0f84b6010000 e8???????? 8b4010 }
            // n = 7, score = 400
            //   57                   | push                edi
            //   e8????????           |                     
            //   83c408               | add                 esp, 8
            //   85c0                 | test                eax, eax
            //   0f84b6010000         | je                  0x1bc
            //   e8????????           |                     
            //   8b4010               | mov                 eax, dword ptr [eax + 0x10]

        $sequence_4 = { 8bf2 8b4338 f76b40 03c8 13f2 0fa4ce01 89757c }
            // n = 7, score = 400
            //   8bf2                 | mov                 esi, edx
            //   8b4338               | mov                 eax, dword ptr [ebx + 0x38]
            //   f76b40               | imul                dword ptr [ebx + 0x40]
            //   03c8                 | add                 ecx, eax
            //   13f2                 | adc                 esi, edx
            //   0fa4ce01             | shld                esi, ecx, 1
            //   89757c               | mov                 dword ptr [ebp + 0x7c], esi

        $sequence_5 = { 8b442424 03c1 89442424 8bc8 8b742424 }
            // n = 5, score = 400
            //   8b442424             | mov                 eax, dword ptr [esp + 0x24]
            //   03c1                 | add                 eax, ecx
            //   89442424             | mov                 dword ptr [esp + 0x24], eax
            //   8bc8                 | mov                 ecx, eax
            //   8b742424             | mov                 esi, dword ptr [esp + 0x24]

        $sequence_6 = { 75f8 2bcb d1f9 41 03c1 57 50 }
            // n = 7, score = 400
            //   75f8                 | jne                 0xfffffffa
            //   2bcb                 | sub                 ecx, ebx
            //   d1f9                 | sar                 ecx, 1
            //   41                   | inc                 ecx
            //   03c1                 | add                 eax, ecx
            //   57                   | push                edi
            //   50                   | push                eax

        $sequence_7 = { 8d4f1f 3bf8 771f 3bce 721b 8bcf 2bf7 }
            // n = 7, score = 400
            //   8d4f1f               | lea                 ecx, [edi + 0x1f]
            //   3bf8                 | cmp                 edi, eax
            //   771f                 | ja                  0x21
            //   3bce                 | cmp                 ecx, esi
            //   721b                 | jb                  0x1d
            //   8bcf                 | mov                 ecx, edi
            //   2bf7                 | sub                 esi, edi

        $sequence_8 = { 85f6 745f 681b040a7a 56 e8???????? 8b0d???????? 6850b21d58 }
            // n = 7, score = 400
            //   85f6                 | test                esi, esi
            //   745f                 | je                  0x61
            //   681b040a7a           | push                0x7a0a041b
            //   56                   | push                esi
            //   e8????????           |                     
            //   8b0d????????         |                     
            //   6850b21d58           | push                0x581db250

        $sequence_9 = { eb64 83ff01 7522 0fb6d1 bf02000000 83e203 0fb6cb }
            // n = 7, score = 400
            //   eb64                 | jmp                 0x66
            //   83ff01               | cmp                 edi, 1
            //   7522                 | jne                 0x24
            //   0fb6d1               | movzx               edx, cl
            //   bf02000000           | mov                 edi, 2
            //   83e203               | and                 edx, 3
            //   0fb6cb               | movzx               ecx, bl

    condition:
        7 of them and filesize < 180224
}

rule win_mailto_w0 { 
    meta: 
        copyright = "(c) 2020 Crowdstrike Inc." 
        author = "Crowdstrike"
        description = "Detects the Netwalker ransomware" 
        reports = "CSIT-20081" 
        source = "https://go.crowdstrike.com/rs/281-OBQ-266/images/ReportCSIT-20081e.pdf"
        version = "202004281747" 
        last_modified = "2020-04-28" 
        malware_family = "Netwalker" 
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.mailto"
        malpedia_rule_date = "20210224"
        malpedia_hash = ""
        malpedia_version = "20210224"
        malpedia_sharing = "TLP:WHITE"
    strings: 
        $salsaconst = "expand 32-byte kexpand 16-byte k" 
        $ins_getapi = {55 8b ec a1 ?? ?? ?? ?? 5d c3} 
        $ins_crc32 = {25 20 83 b8 ed 33 d0} 
        $ins_push1137 = {68 39 05 00 00 68 69 7a 00 00} 
        $ins_rc4 = {8b 45 ( e? | f? ) 83 c0 01 33 d2 b9 00 01 00 00 f7 f1 89 55} 
        $in_c25519 = {6a 00 68 41 db 01 00} 
    condition: 
        3 of them
}

rule win_mailto_w1 { 
    meta: 
        copyright = "(c) 2020 Crowdstrike Inc." 
        author = "Crowdstrike"
        description = "Detects the Netwalker ransomware" 
        reports = "CSIT-20081" 
        source = "https://go.crowdstrike.com/rs/281-OBQ-266/images/ReportCSIT-20081e.pdf"
        version = "202004281748" 
        last_modified = "2020-04-28" 
        malware_family = "Netwalker" 
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.mailto"
        malpedia_rule_date = "20210224"
        malpedia_hash = ""
        malpedia_version = "20210224"
        malpedia_sharing = "TLP:WHITE"
    strings: 
        $ = "namesz" fullword 
        $ = "crmask" fullword 
        $ = "idsz" fullword 
        $ = "lend" fullword 
        $ = "lfile" fullword 
        $ = "mpk" fullword 
        $ = "namesz" fullword 
        $ = "pspath" fullword 
        $ = "rwsz" fullword 
        $ = "spsz" fullword 
        $ = "svcwait" fullword 
        $ = "unlocker" fullword 
        $ = "onion1" fullword 
    condition: 10 of them
}