SYMBOLCOMMON_NAMEaka. SYNONYMS
win.nexster_bot (Back to overview)

Nexster Bot


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References
2016-10-20Twitter (@benkow_)Benoît Ancel
@online{ancel:20161020:nexter91:909eaee, author = {Benoît Ancel}, title = {{Tweet on nexter91 Panel}}, date = {2016-10-20}, organization = {Twitter (@benkow_)}, url = {https://twitter.com/benkow_/status/789006720668405760}, language = {English}, urldate = {2020-01-07} } Tweet on nexter91 Panel
Nexster Bot
Yara Rules
[TLP:WHITE] win_nexster_bot_auto (20220411 | Detects win.nexster_bot.)
rule win_nexster_bot_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        version = "1"
        description = "Detects win.nexster_bot."
        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.nexster_bot"
        malpedia_rule_date = "20220405"
        malpedia_hash = "ecd38294bd47d5589be5cd5490dc8bb4804afc2a"
        malpedia_version = "20220411"
        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 = { e8???????? 8b6c2418 8d44241c 3be8 }
            // n = 4, score = 100
            //   e8????????           |                     
            //   8b6c2418             | mov                 ebp, dword ptr [esp + 0x18]
            //   8d44241c             | lea                 eax, dword ptr [esp + 0x1c]
            //   3be8                 | cmp                 ebp, eax

        $sequence_1 = { 40 84c9 75f9 8dbc240c010000 2bc2 }
            // n = 5, score = 100
            //   40                   | inc                 eax
            //   84c9                 | test                cl, cl
            //   75f9                 | jne                 0xfffffffb
            //   8dbc240c010000       | lea                 edi, dword ptr [esp + 0x10c]
            //   2bc2                 | sub                 eax, edx

        $sequence_2 = { 898c24b0010000 8a0d???????? 899424b4010000 66898424b8010000 }
            // n = 4, score = 100
            //   898c24b0010000       | mov                 dword ptr [esp + 0x1b0], ecx
            //   8a0d????????         |                     
            //   899424b4010000       | mov                 dword ptr [esp + 0x1b4], edx
            //   66898424b8010000     | mov                 word ptr [esp + 0x1b8], ax

        $sequence_3 = { 8b74240c ba???????? 8bc6 2bd6 8bff 8a08 880c02 }
            // n = 7, score = 100
            //   8b74240c             | mov                 esi, dword ptr [esp + 0xc]
            //   ba????????           |                     
            //   8bc6                 | mov                 eax, esi
            //   2bd6                 | sub                 edx, esi
            //   8bff                 | mov                 edi, edi
            //   8a08                 | mov                 cl, byte ptr [eax]
            //   880c02               | mov                 byte ptr [edx + eax], cl

        $sequence_4 = { 8d85bc010000 50 8d4dd0 e8???????? }
            // n = 4, score = 100
            //   8d85bc010000         | lea                 eax, dword ptr [ebp + 0x1bc]
            //   50                   | push                eax
            //   8d4dd0               | lea                 ecx, dword ptr [ebp - 0x30]
            //   e8????????           |                     

        $sequence_5 = { 8d842480000000 50 ff15???????? 8b3d???????? }
            // n = 4, score = 100
            //   8d842480000000       | lea                 eax, dword ptr [esp + 0x80]
            //   50                   | push                eax
            //   ff15????????         |                     
            //   8b3d????????         |                     

        $sequence_6 = { 8b842498000000 6a0a 8d542410 52 50 e8???????? 8b9424a8000000 }
            // n = 7, score = 100
            //   8b842498000000       | mov                 eax, dword ptr [esp + 0x98]
            //   6a0a                 | push                0xa
            //   8d542410             | lea                 edx, dword ptr [esp + 0x10]
            //   52                   | push                edx
            //   50                   | push                eax
            //   e8????????           |                     
            //   8b9424a8000000       | mov                 edx, dword ptr [esp + 0xa8]

        $sequence_7 = { ff15???????? 83f8ff 751c 57 }
            // n = 4, score = 100
            //   ff15????????         |                     
            //   83f8ff               | cmp                 eax, -1
            //   751c                 | jne                 0x1e
            //   57                   | push                edi

        $sequence_8 = { 8a0d???????? 899424b4010000 66898424b8010000 888c24ba010000 e9???????? 83f802 0f853b020000 }
            // n = 7, score = 100
            //   8a0d????????         |                     
            //   899424b4010000       | mov                 dword ptr [esp + 0x1b4], edx
            //   66898424b8010000     | mov                 word ptr [esp + 0x1b8], ax
            //   888c24ba010000       | mov                 byte ptr [esp + 0x1ba], cl
            //   e9????????           |                     
            //   83f802               | cmp                 eax, 2
            //   0f853b020000         | jne                 0x241

        $sequence_9 = { 8d842418030000 50 6a00 ff15???????? 8b35???????? 8d8c2410020000 51 }
            // n = 7, score = 100
            //   8d842418030000       | lea                 eax, dword ptr [esp + 0x318]
            //   50                   | push                eax
            //   6a00                 | push                0
            //   ff15????????         |                     
            //   8b35????????         |                     
            //   8d8c2410020000       | lea                 ecx, dword ptr [esp + 0x210]
            //   51                   | push                ecx

    condition:
        7 of them and filesize < 245760
}
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