SYMBOLCOMMON_NAMEaka. SYNONYMS
win.virdetdoor (Back to overview)

virdetdoor


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References
2016-01-28ProofpointDarien Huss
@online{huss:20160128:exploring:7f85d44, author = {Darien Huss}, title = {{Exploring Bergard: Old Malware with New Tricks}}, date = {2016-01-28}, organization = {Proofpoint}, url = {https://www.proofpoint.com/us/exploring-bergard-old-malware-new-tricks}, language = {English}, urldate = {2019-12-20} } Exploring Bergard: Old Malware with New Tricks
virdetdoor Codoso
Yara Rules
[TLP:WHITE] win_virdetdoor_auto (20220808 | Detects win.virdetdoor.)
rule win_virdetdoor_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-08-05"
        version = "1"
        description = "Detects win.virdetdoor."
        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.virdetdoor"
        malpedia_rule_date = "20220805"
        malpedia_hash = "6ec06c64bcfdbeda64eff021c766b4ce34542b71"
        malpedia_version = "20220808"
        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 = { 3bf0 7d17 8b8bac020000 2bc6 50 8d0431 50 }
            // n = 7, score = 100
            //   3bf0                 | cmp                 esi, eax
            //   7d17                 | jge                 0x19
            //   8b8bac020000         | mov                 ecx, dword ptr [ebx + 0x2ac]
            //   2bc6                 | sub                 eax, esi
            //   50                   | push                eax
            //   8d0431               | lea                 eax, [ecx + esi]
            //   50                   | push                eax

        $sequence_1 = { 8d4fc3 83f905 7760 85f6 7437 }
            // n = 5, score = 100
            //   8d4fc3               | lea                 ecx, [edi - 0x3d]
            //   83f905               | cmp                 ecx, 5
            //   7760                 | ja                  0x62
            //   85f6                 | test                esi, esi
            //   7437                 | je                  0x39

        $sequence_2 = { 7737 8b75fc 83fb03 740a 8a06 46 }
            // n = 6, score = 100
            //   7737                 | ja                  0x39
            //   8b75fc               | mov                 esi, dword ptr [ebp - 4]
            //   83fb03               | cmp                 ebx, 3
            //   740a                 | je                  0xc
            //   8a06                 | mov                 al, byte ptr [esi]
            //   46                   | inc                 esi

        $sequence_3 = { 83c40c 66c70645cc 33c0 66c7460840ff 40 }
            // n = 5, score = 100
            //   83c40c               | add                 esp, 0xc
            //   66c70645cc           | mov                 word ptr [esi], 0xcc45
            //   33c0                 | xor                 eax, eax
            //   66c7460840ff         | mov                 word ptr [esi + 8], 0xff40
            //   40                   | inc                 eax

        $sequence_4 = { 7462 0fb7560c 8b442410 c1ea04 83e20f 8d0490 89442418 }
            // n = 7, score = 100
            //   7462                 | je                  0x64
            //   0fb7560c             | movzx               edx, word ptr [esi + 0xc]
            //   8b442410             | mov                 eax, dword ptr [esp + 0x10]
            //   c1ea04               | shr                 edx, 4
            //   83e20f               | and                 edx, 0xf
            //   8d0490               | lea                 eax, [eax + edx*4]
            //   89442418             | mov                 dword ptr [esp + 0x18], eax

        $sequence_5 = { 8b7d10 57 7434 8b35???????? ffd6 50 8d45cc }
            // n = 7, score = 100
            //   8b7d10               | mov                 edi, dword ptr [ebp + 0x10]
            //   57                   | push                edi
            //   7434                 | je                  0x36
            //   8b35????????         |                     
            //   ffd6                 | call                esi
            //   50                   | push                eax
            //   8d45cc               | lea                 eax, [ebp - 0x34]

        $sequence_6 = { c1e808 0bd0 8a4508 884327 816324000000ff }
            // n = 5, score = 100
            //   c1e808               | shr                 eax, 8
            //   0bd0                 | or                  edx, eax
            //   8a4508               | mov                 al, byte ptr [ebp + 8]
            //   884327               | mov                 byte ptr [ebx + 0x27], al
            //   816324000000ff       | and                 dword ptr [ebx + 0x24], 0xff000000

        $sequence_7 = { 50 ffd6 83c418 803f3a }
            // n = 4, score = 100
            //   50                   | push                eax
            //   ffd6                 | call                esi
            //   83c418               | add                 esp, 0x18
            //   803f3a               | cmp                 byte ptr [edi], 0x3a

        $sequence_8 = { 56 6a28 33c0 5a }
            // n = 4, score = 100
            //   56                   | push                esi
            //   6a28                 | push                0x28
            //   33c0                 | xor                 eax, eax
            //   5a                   | pop                 edx

        $sequence_9 = { 6a44 5a 8bcb e8???????? 83c410 8bf8 85ff }
            // n = 7, score = 100
            //   6a44                 | push                0x44
            //   5a                   | pop                 edx
            //   8bcb                 | mov                 ecx, ebx
            //   e8????????           |                     
            //   83c410               | add                 esp, 0x10
            //   8bf8                 | mov                 edi, eax
            //   85ff                 | test                edi, edi

    condition:
        7 of them and filesize < 106496
}
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