rule win_outlook_backdoor_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        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 = "20230124"
        malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686"
        malpedia_version = "20230125"
        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 = { ff30 8d75e0 e8???????? 8b08 894d18 8b4004 83c410 }
            // n = 7, score = 600
            //   ff30                 | push                dword ptr [eax]
            //   8d75e0               | lea                 esi, [ebp - 0x20]
            //   e8????????           |                     
            //   8b08                 | mov                 ecx, dword ptr [eax]
            //   894d18               | mov                 dword ptr [ebp + 0x18], ecx
            //   8b4004               | mov                 eax, dword ptr [eax + 4]
            //   83c410               | add                 esp, 0x10

        $sequence_1 = { e8???????? 83c40c a1???????? 8b4df4 5f 5e 64890d00000000 }
            // n = 7, score = 600
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   a1????????           |                     
            //   8b4df4               | mov                 ecx, dword ptr [ebp - 0xc]
            //   5f                   | pop                 edi
            //   5e                   | pop                 esi
            //   64890d00000000       | mov                 dword ptr fs:[0], ecx

        $sequence_2 = { ff7004 8d75d8 ff30 e8???????? 8b08 ff75e8 }
            // n = 6, score = 600
            //   ff7004               | push                dword ptr [eax + 4]
            //   8d75d8               | lea                 esi, [ebp - 0x28]
            //   ff30                 | push                dword ptr [eax]
            //   e8????????           |                     
            //   8b08                 | mov                 ecx, dword ptr [eax]
            //   ff75e8               | push                dword ptr [ebp - 0x18]

        $sequence_3 = { 8d4dd4 e9???????? 8d75b8 e9???????? 8d758c }
            // n = 5, score = 600
            //   8d4dd4               | lea                 ecx, [ebp - 0x2c]
            //   e9????????           |                     
            //   8d75b8               | lea                 esi, [ebp - 0x48]
            //   e9????????           |                     
            //   8d758c               | lea                 esi, [ebp - 0x74]

        $sequence_4 = { 7522 ff750c 8bcf ff7508 e8???????? 56 6a01 }
            // n = 7, score = 600
            //   7522                 | jne                 0x24
            //   ff750c               | push                dword ptr [ebp + 0xc]
            //   8bcf                 | mov                 ecx, edi
            //   ff7508               | push                dword ptr [ebp + 8]
            //   e8????????           |                     
            //   56                   | push                esi
            //   6a01                 | push                1

        $sequence_5 = { 52 e8???????? 6a0c e8???????? 8bf0 59 59 }
            // n = 7, score = 600
            //   52                   | push                edx
            //   e8????????           |                     
            //   6a0c                 | push                0xc
            //   e8????????           |                     
            //   8bf0                 | mov                 esi, eax
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx

        $sequence_6 = { 51 51 53 56 57 8965f0 6a5c }
            // n = 7, score = 600
            //   51                   | push                ecx
            //   51                   | push                ecx
            //   53                   | push                ebx
            //   56                   | push                esi
            //   57                   | push                edi
            //   8965f0               | mov                 dword ptr [ebp - 0x10], esp
            //   6a5c                 | push                0x5c

        $sequence_7 = { 50 33c0 40 894d08 e8???????? 5b 5d }
            // n = 7, score = 600
            //   50                   | push                eax
            //   33c0                 | xor                 eax, eax
            //   40                   | inc                 eax
            //   894d08               | mov                 dword ptr [ebp + 8], ecx
            //   e8????????           |                     
            //   5b                   | pop                 ebx
            //   5d                   | pop                 ebp

        $sequence_8 = { 8b4d0c 832100 57 8d3c06 8975f8 3bf7 7373 }
            // n = 7, score = 600
            //   8b4d0c               | mov                 ecx, dword ptr [ebp + 0xc]
            //   832100               | and                 dword ptr [ecx], 0
            //   57                   | push                edi
            //   8d3c06               | lea                 edi, [esi + eax]
            //   8975f8               | mov                 dword ptr [ebp - 8], esi
            //   3bf7                 | cmp                 esi, edi
            //   7373                 | jae                 0x75

        $sequence_9 = { 8b4518 895de0 897de4 8945ec }
            // n = 4, score = 600
            //   8b4518               | mov                 eax, dword ptr [ebp + 0x18]
            //   895de0               | mov                 dword ptr [ebp - 0x20], ebx
            //   897de4               | mov                 dword ptr [ebp - 0x1c], edi
            //   8945ec               | mov                 dword ptr [ebp - 0x14], eax

    condition:
        7 of them and filesize < 2912256
}