rule win_outlook_backdoor_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        version = "1"
        description = "Detects win.outlook_backdoor."
        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.outlook_backdoor"
        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 = { 83c40c 8945e8 85c0 7503 214520 837dac10 8b4598 }
            // n = 7, score = 600
            //   83c40c               | add                 esp, 0xc
            //   8945e8               | mov                 dword ptr [ebp - 0x18], eax
            //   85c0                 | test                eax, eax
            //   7503                 | jne                 5
            //   214520               | and                 dword ptr [ebp + 0x20], eax
            //   837dac10             | cmp                 dword ptr [ebp - 0x54], 0x10
            //   8b4598               | mov                 eax, dword ptr [ebp - 0x68]

        $sequence_1 = { 8d4608 6a00 6880000000 6a02 6a00 6a01 68000000c0 }
            // n = 7, score = 600
            //   8d4608               | lea                 eax, dword ptr [esi + 8]
            //   6a00                 | push                0
            //   6880000000           | push                0x80
            //   6a02                 | push                2
            //   6a00                 | push                0
            //   6a01                 | push                1
            //   68000000c0           | push                0xc0000000

        $sequence_2 = { 8b4704 894004 83670800 3b5f04 741c 55 56 }
            // n = 7, score = 600
            //   8b4704               | mov                 eax, dword ptr [edi + 4]
            //   894004               | mov                 dword ptr [eax + 4], eax
            //   83670800             | and                 dword ptr [edi + 8], 0
            //   3b5f04               | cmp                 ebx, dword ptr [edi + 4]
            //   741c                 | je                  0x1e
            //   55                   | push                ebp
            //   56                   | push                esi

        $sequence_3 = { ff7528 ff75dc ff7524 50 8b4514 e8???????? 8b08 }
            // n = 7, score = 600
            //   ff7528               | push                dword ptr [ebp + 0x28]
            //   ff75dc               | push                dword ptr [ebp - 0x24]
            //   ff7524               | push                dword ptr [ebp + 0x24]
            //   50                   | push                eax
            //   8b4514               | mov                 eax, dword ptr [ebp + 0x14]
            //   e8????????           |                     
            //   8b08                 | mov                 ecx, dword ptr [eax]

        $sequence_4 = { 53 ff7004 ff30 53 51 ff5214 8bf0 }
            // n = 7, score = 600
            //   53                   | push                ebx
            //   ff7004               | push                dword ptr [eax + 4]
            //   ff30                 | push                dword ptr [eax]
            //   53                   | push                ebx
            //   51                   | push                ecx
            //   ff5214               | call                dword ptr [edx + 0x14]
            //   8bf0                 | mov                 esi, eax

        $sequence_5 = { 6a00 8d45d0 e8???????? eb16 8b75ec 6aff 6a00 }
            // n = 7, score = 600
            //   6a00                 | push                0
            //   8d45d0               | lea                 eax, dword ptr [ebp - 0x30]
            //   e8????????           |                     
            //   eb16                 | jmp                 0x18
            //   8b75ec               | mov                 esi, dword ptr [ebp - 0x14]
            //   6aff                 | push                -1
            //   6a00                 | push                0

        $sequence_6 = { 83ec2c 56 57 ff750c 8d7308 ff7508 8b06 }
            // n = 7, score = 600
            //   83ec2c               | sub                 esp, 0x2c
            //   56                   | push                esi
            //   57                   | push                edi
            //   ff750c               | push                dword ptr [ebp + 0xc]
            //   8d7308               | lea                 esi, dword ptr [ebx + 8]
            //   ff7508               | push                dword ptr [ebp + 8]
            //   8b06                 | mov                 eax, dword ptr [esi]

        $sequence_7 = { e8???????? 8b4508 83c428 5f 5e 5b 8be5 }
            // n = 7, score = 600
            //   e8????????           |                     
            //   8b4508               | mov                 eax, dword ptr [ebp + 8]
            //   83c428               | add                 esp, 0x28
            //   5f                   | pop                 edi
            //   5e                   | pop                 esi
            //   5b                   | pop                 ebx
            //   8be5                 | mov                 esp, ebp

        $sequence_8 = { 59 8945ec 8365fc00 33db 43 85c0 7424 }
            // n = 7, score = 600
            //   59                   | pop                 ecx
            //   8945ec               | mov                 dword ptr [ebp - 0x14], eax
            //   8365fc00             | and                 dword ptr [ebp - 4], 0
            //   33db                 | xor                 ebx, ebx
            //   43                   | inc                 ebx
            //   85c0                 | test                eax, eax
            //   7424                 | je                  0x26

        $sequence_9 = { 89442410 7e70 0fb640ff 8b17 50 8bcf }
            // n = 6, score = 600
            //   89442410             | mov                 dword ptr [esp + 0x10], eax
            //   7e70                 | jle                 0x72
            //   0fb640ff             | movzx               eax, byte ptr [eax - 1]
            //   8b17                 | mov                 edx, dword ptr [edi]
            //   50                   | push                eax
            //   8bcf                 | mov                 ecx, edi

    condition:
        7 of them and filesize < 2912256
}