SYMBOLCOMMON_NAMEaka. SYNONYMS
win.brbbot (Back to overview)

BrbBot


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References
2022-02-08Itay Migdal
@online{migdal:20220208:brbbot:5172f60, author = {Itay Migdal}, title = {{Brbbot Analysis}}, date = {2022-02-08}, url = {https://github.com/itaymigdal/malware-analysis-writeups/blob/main/Brbbot/Brbbot.md}, language = {English}, urldate = {2022-02-09} } Brbbot Analysis
BrbBot
Yara Rules
[TLP:WHITE] win_brbbot_auto (20230407 | Detects win.brbbot.)
rule win_brbbot_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-03-28"
        version = "1"
        description = "Detects win.brbbot."
        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.brbbot"
        malpedia_rule_date = "20230328"
        malpedia_hash = "9d2d75cef573c1c2d861f5197df8f563b05a305d"
        malpedia_version = "20230407"
        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 = { 488905???????? ff15???????? 488bc8 ff15???????? 488d1574450000 488bce }
            // n = 6, score = 100
            //   488905????????       |                     
            //   ff15????????         |                     
            //   488bc8               | mov                 esi, edi
            //   ff15????????         |                     
            //   488d1574450000       | dec                 ecx
            //   488bce               | sar                 esi, 5

        $sequence_1 = { 7406 ff15???????? 85ff 790d 85ed }
            // n = 5, score = 100
            //   7406                 | arpl                cx, cx
            //   ff15????????         |                     
            //   85ff                 | dec                 eax
            //   790d                 | lea                 edx, [eax + ecx*8]
            //   85ed                 | inc                 edx

        $sequence_2 = { 488b5540 488b5d28 4883c9ff 488bfa 33c0 f2ae 48f7d1 }
            // n = 7, score = 100
            //   488b5540             | test                eax, eax
            //   488b5d28             | je                  0x9c6
            //   4883c9ff             | mov                 edx, 8
            //   488bfa               | inc                 ecx
            //   33c0                 | mov                 eax, 0x3e8
            //   f2ae                 | dec                 eax
            //   48f7d1               | mov                 ecx, eax

        $sequence_3 = { 7404 f0440108 488d4158 41b806000000 488d15fab60000 }
            // n = 5, score = 100
            //   7404                 | dec                 eax
            //   f0440108             | add                 ebx, eax
            //   488d4158             | jmp                 0xf32
            //   41b806000000         | dec                 ebx
            //   488d15fab60000       | mov                 eax, dword ptr [eax + edi*8 + 0x15ac0]

        $sequence_4 = { 488d0d7dde0000 e8???????? 85c0 740e ba01000000 488bcd }
            // n = 6, score = 100
            //   488d0d7dde0000       | dec                 eax
            //   e8????????           |                     
            //   85c0                 | or                  ecx, 0xffffffff
            //   740e                 | dec                 eax
            //   ba01000000           | mov                 edi, ebp
            //   488bcd               | dec                 eax

        $sequence_5 = { 33d2 ff15???????? 4c8b7c2458 4d85ed 7430 4883c9ff }
            // n = 6, score = 100
            //   33d2                 | dec                 eax
            //   ff15????????         |                     
            //   4c8b7c2458           | lea                 edi, [0x10432]
            //   4d85ed               | dec                 eax
            //   7430                 | lea                 esi, [0x1042f]
            //   4883c9ff             | inc                 ecx

        $sequence_6 = { 8bd9 ff15???????? 4c8d4304 ba08000000 488bc8 ff15???????? 448b442420 }
            // n = 7, score = 100
            //   8bd9                 | dec                 eax
            //   ff15????????         |                     
            //   4c8d4304             | mov                 ecx, eax
            //   ba08000000           | dec                 eax
            //   488bc8               | mov                 dword ptr [ebp], eax
            //   ff15????????         |                     
            //   448b442420           | dec                 eax

        $sequence_7 = { 4883c9ff 85c0 757a 33c0 41c70701000000 498dbe04010000 }
            // n = 6, score = 100
            //   4883c9ff             | jne                 0x122c
            //   85c0                 | dec                 esp
            //   757a                 | mov                 dword ptr [eax - 0x28], ebp
            //   33c0                 | inc                 ecx
            //   41c70701000000       | mov                 ebp, 1
            //   498dbe04010000       | dec                 eax

        $sequence_8 = { 81fffc000000 0f84b8010000 488d2dbdbe0000 41bc14030000 4c8d0560780000 488bcd 418bd4 }
            // n = 7, score = 100
            //   81fffc000000         | mov                 edi, esp
            //   0f84b8010000         | inc                 ecx
            //   488d2dbdbe0000       | mov                 eax, 0x103
            //   41bc14030000         | mov                 byte ptr [esp + 0x40], 0
            //   4c8d0560780000       | xor                 ecx, ecx
            //   488bcd               | dec                 eax
            //   418bd4               | mov                 dword ptr [esp + 0x30], 0

        $sequence_9 = { 33d2 488bce e8???????? ff15???????? 4c8bc6 488bc8 33d2 }
            // n = 7, score = 100
            //   33d2                 | inc                 ebp
            //   488bce               | mov                 eax, ebp
            //   e8????????           |                     
            //   ff15????????         |                     
            //   4c8bc6               | inc                 ecx
            //   488bc8               | mov                 edx, ebp
            //   33d2                 | dec                 eax

    condition:
        7 of them and filesize < 198656
}
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