rule win_outlook_backdoor_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        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 = "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 = { 83c40c 8d5c0302 6a00 6a01 8d4dd4 e8???????? 8bc3 }
            // n = 7, score = 600
            //   83c40c               | add                 esp, 0xc
            //   8d5c0302             | lea                 ebx, [ebx + eax + 2]
            //   6a00                 | push                0
            //   6a01                 | push                1
            //   8d4dd4               | lea                 ecx, [ebp - 0x2c]
            //   e8????????           |                     
            //   8bc3                 | mov                 eax, ebx

        $sequence_1 = { 8b01 83c410 ff5004 6a01 884518 ff7518 8d75cc }
            // n = 7, score = 600
            //   8b01                 | mov                 eax, dword ptr [ecx]
            //   83c410               | add                 esp, 0x10
            //   ff5004               | call                dword ptr [eax + 4]
            //   6a01                 | push                1
            //   884518               | mov                 byte ptr [ebp + 0x18], al
            //   ff7518               | push                dword ptr [ebp + 0x18]
            //   8d75cc               | lea                 esi, [ebp - 0x34]

        $sequence_2 = { 8a06 84c0 75df 803e00 0f842e010000 46 c645f400 }
            // n = 7, score = 600
            //   8a06                 | mov                 al, byte ptr [esi]
            //   84c0                 | test                al, al
            //   75df                 | jne                 0xffffffe1
            //   803e00               | cmp                 byte ptr [esi], 0
            //   0f842e010000         | je                  0x134
            //   46                   | inc                 esi
            //   c645f400             | mov                 byte ptr [ebp - 0xc], 0

        $sequence_3 = { 68000000c0 50 ff15???????? 83f8ff 8906 0f95c0 c3 }
            // n = 7, score = 600
            //   68000000c0           | push                0xc0000000
            //   50                   | push                eax
            //   ff15????????         |                     
            //   83f8ff               | cmp                 eax, -1
            //   8906                 | mov                 dword ptr [esi], eax
            //   0f95c0               | setne               al
            //   c3                   | ret                 

        $sequence_4 = { ff7508 ff75ec 51 52 e8???????? 8b5e08 8b4e04 }
            // n = 7, score = 600
            //   ff7508               | push                dword ptr [ebp + 8]
            //   ff75ec               | push                dword ptr [ebp - 0x14]
            //   51                   | push                ecx
            //   52                   | push                edx
            //   e8????????           |                     
            //   8b5e08               | mov                 ebx, dword ptr [esi + 8]
            //   8b4e04               | mov                 ecx, dword ptr [esi + 4]

        $sequence_5 = { ff7508 e8???????? 8b4df4 b001 5b 64890d00000000 c9 }
            // n = 7, score = 600
            //   ff7508               | push                dword ptr [ebp + 8]
            //   e8????????           |                     
            //   8b4df4               | mov                 ecx, dword ptr [ebp - 0xc]
            //   b001                 | mov                 al, 1
            //   5b                   | pop                 ebx
            //   64890d00000000       | mov                 dword ptr fs:[0], ecx
            //   c9                   | leave               

        $sequence_6 = { ff5744 8bf0 e8???????? 5f 5e c20400 55 }
            // n = 7, score = 600
            //   ff5744               | call                dword ptr [edi + 0x44]
            //   8bf0                 | mov                 esi, eax
            //   e8????????           |                     
            //   5f                   | pop                 edi
            //   5e                   | pop                 esi
            //   c20400               | ret                 4
            //   55                   | push                ebp

        $sequence_7 = { e8???????? 83ec20 8365f000 56 8bf1 6a00 8d4dd4 }
            // n = 7, score = 600
            //   e8????????           |                     
            //   83ec20               | sub                 esp, 0x20
            //   8365f000             | and                 dword ptr [ebp - 0x10], 0
            //   56                   | push                esi
            //   8bf1                 | mov                 esi, ecx
            //   6a00                 | push                0
            //   8d4dd4               | lea                 ecx, [ebp - 0x2c]

        $sequence_8 = { 50 56 53 53 ff15???????? ff742410 8d4c2420 }
            // n = 7, score = 600
            //   50                   | push                eax
            //   56                   | push                esi
            //   53                   | push                ebx
            //   53                   | push                ebx
            //   ff15????????         |                     
            //   ff742410             | push                dword ptr [esp + 0x10]
            //   8d4c2420             | lea                 ecx, [esp + 0x20]

        $sequence_9 = { ff750c e8???????? 83c40c 85c0 7517 8b45fc 0fb61c18 }
            // n = 7, score = 600
            //   ff750c               | push                dword ptr [ebp + 0xc]
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   85c0                 | test                eax, eax
            //   7517                 | jne                 0x19
            //   8b45fc               | mov                 eax, dword ptr [ebp - 4]
            //   0fb61c18             | movzx               ebx, byte ptr [eax + ebx]

    condition:
        7 of them and filesize < 2912256
}