rule win_outlook_backdoor_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2021-06-10"
        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 = "20210604"
        malpedia_hash = "be09d5d71e77373c0f538068be31a2ad4c69cfbd"
        malpedia_version = "20210616"
        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 = { 57 56 8d7584 e8???????? 33f6 46 f6455401 }
            // n = 7, score = 500
            //   57                   | push                edi
            //   56                   | push                esi
            //   8d7584               | lea                 esi, dword ptr [ebp - 0x7c]
            //   e8????????           |                     
            //   33f6                 | xor                 esi, esi
            //   46                   | inc                 esi
            //   f6455401             | test                byte ptr [ebp + 0x54], 1

        $sequence_1 = { e8???????? 56 57 8b7d08 8365fc00 8d7734 e8???????? }
            // n = 7, score = 500
            //   e8????????           |                     
            //   56                   | push                esi
            //   57                   | push                edi
            //   8b7d08               | mov                 edi, dword ptr [ebp + 8]
            //   8365fc00             | and                 dword ptr [ebp - 4], 0
            //   8d7734               | lea                 esi, dword ptr [edi + 0x34]
            //   e8????????           |                     

        $sequence_2 = { 64890d00000000 5b 8be5 5d c3 56 8d7760 }
            // n = 7, score = 500
            //   64890d00000000       | mov                 dword ptr fs:[0], ecx
            //   5b                   | pop                 ebx
            //   8be5                 | mov                 esp, ebp
            //   5d                   | pop                 ebp
            //   c3                   | ret                 
            //   56                   | push                esi
            //   8d7760               | lea                 esi, dword ptr [edi + 0x60]

        $sequence_3 = { 8b4508 83783410 7205 8b4020 eb03 83c020 8bcf }
            // n = 7, score = 500
            //   8b4508               | mov                 eax, dword ptr [ebp + 8]
            //   83783410             | cmp                 dword ptr [eax + 0x34], 0x10
            //   7205                 | jb                  7
            //   8b4020               | mov                 eax, dword ptr [eax + 0x20]
            //   eb03                 | jmp                 5
            //   83c020               | add                 eax, 0x20
            //   8bcf                 | mov                 ecx, edi

        $sequence_4 = { ff7518 8d45e0 ff75d8 ff7514 50 8bc3 e8???????? }
            // n = 7, score = 500
            //   ff7518               | push                dword ptr [ebp + 0x18]
            //   8d45e0               | lea                 eax, dword ptr [ebp - 0x20]
            //   ff75d8               | push                dword ptr [ebp - 0x28]
            //   ff7514               | push                dword ptr [ebp + 0x14]
            //   50                   | push                eax
            //   8bc3                 | mov                 eax, ebx
            //   e8????????           |                     

        $sequence_5 = { e8???????? 8b00 3b4704 7411 8b4df8 83c10c 8bc3 }
            // n = 7, score = 500
            //   e8????????           |                     
            //   8b00                 | mov                 eax, dword ptr [eax]
            //   3b4704               | cmp                 eax, dword ptr [edi + 4]
            //   7411                 | je                  0x13
            //   8b4df8               | mov                 ecx, dword ptr [ebp - 8]
            //   83c10c               | add                 ecx, 0xc
            //   8bc3                 | mov                 eax, ebx

        $sequence_6 = { e8???????? 83c410 53 6a01 8d4dcc e8???????? 8bc6 }
            // n = 7, score = 500
            //   e8????????           |                     
            //   83c410               | add                 esp, 0x10
            //   53                   | push                ebx
            //   6a01                 | push                1
            //   8d4dcc               | lea                 ecx, dword ptr [ebp - 0x34]
            //   e8????????           |                     
            //   8bc6                 | mov                 eax, esi

        $sequence_7 = { 3bf7 0f95c0 5e c20400 55 8bec }
            // n = 6, score = 500
            //   3bf7                 | cmp                 esi, edi
            //   0f95c0               | setne               al
            //   5e                   | pop                 esi
            //   c20400               | ret                 4
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp

        $sequence_8 = { 5e c20400 8325????????00 53 56 57 8bf9 }
            // n = 7, score = 500
            //   5e                   | pop                 esi
            //   c20400               | ret                 4
            //   8325????????00       |                     
            //   53                   | push                ebx
            //   56                   | push                esi
            //   57                   | push                edi
            //   8bf9                 | mov                 edi, ecx

        $sequence_9 = { 7413 ff7608 8bc1 e8???????? ff7604 e8???????? 59 }
            // n = 7, score = 500
            //   7413                 | je                  0x15
            //   ff7608               | push                dword ptr [esi + 8]
            //   8bc1                 | mov                 eax, ecx
            //   e8????????           |                     
            //   ff7604               | push                dword ptr [esi + 4]
            //   e8????????           |                     
            //   59                   | pop                 ecx

    condition:
        7 of them and filesize < 2912256
}