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win.corebot (Back to overview)

Corebot


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References
Yara Rules
[TLP:WHITE] win_corebot_auto (20200529 | autogenerated rule brought to you by yara-signator)
rule win_corebot_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2020-05-30"
        version = "1"
        description = "autogenerated rule brought to you by yara-signator"
        tool = "yara-signator v0.4.0"
        tool_config = "callsandjumps;datarefs;binvalue"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.corebot"
        malpedia_rule_date = "20200529"
        malpedia_hash = "92c362319514e5a6da26204961446caa3a8b32a8"
        malpedia_version = "20200529"
        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 / approach 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 = { ebfa 55 89e5 53 57 56 83ec0c }
            // n = 7, score = 1100
            //   ebfa                 | jmp                 0xfffffffc
            //   55                   | push                ebp
            //   89e5                 | mov                 ebp, esp
            //   53                   | push                ebx
            //   57                   | push                edi
            //   56                   | push                esi
            //   83ec0c               | sub                 esp, 0xc

        $sequence_1 = { 8918 89f0 83c40c 5e 5f 5b 5d }
            // n = 7, score = 1100
            //   8918                 | mov                 dword ptr [eax], ebx
            //   89f0                 | mov                 eax, esi
            //   83c40c               | add                 esp, 0xc
            //   5e                   | pop                 esi
            //   5f                   | pop                 edi
            //   5b                   | pop                 ebx
            //   5d                   | pop                 ebp

        $sequence_2 = { 83e601 31c0 40 8932 5e c3 31c0 }
            // n = 7, score = 1100
            //   83e601               | and                 esi, 1
            //   31c0                 | xor                 eax, eax
            //   40                   | inc                 eax
            //   8932                 | mov                 dword ptr [edx], esi
            //   5e                   | pop                 esi
            //   c3                   | ret                 
            //   31c0                 | xor                 eax, eax

        $sequence_3 = { 8945f0 50 57 53 e8???????? 83c410 }
            // n = 6, score = 1100
            //   8945f0               | mov                 dword ptr [ebp - 0x10], eax
            //   50                   | push                eax
            //   57                   | push                edi
            //   53                   | push                ebx
            //   e8????????           |                     
            //   83c410               | add                 esp, 0x10

        $sequence_4 = { 7410 85c0 740c 50 }
            // n = 4, score = 1100
            //   7410                 | je                  0x12
            //   85c0                 | test                eax, eax
            //   740c                 | je                  0xe
            //   50                   | push                eax

        $sequence_5 = { 43 8b4dec 8d55f0 e8???????? 85db 7827 }
            // n = 6, score = 1100
            //   43                   | inc                 ebx
            //   8b4dec               | mov                 ecx, dword ptr [ebp - 0x14]
            //   8d55f0               | lea                 edx, [ebp - 0x10]
            //   e8????????           |                     
            //   85db                 | test                ebx, ebx
            //   7827                 | js                  0x29

        $sequence_6 = { 8035????????df 8035????????e0 8035????????e1 8035????????e2 8035????????e3 }
            // n = 5, score = 1100
            //   8035????????df       |                     
            //   8035????????e0       |                     
            //   8035????????e1       |                     
            //   8035????????e2       |                     
            //   8035????????e3       |                     

        $sequence_7 = { 5b 5d c3 8b7304 31c0 83fe18 72ee }
            // n = 7, score = 1100
            //   5b                   | pop                 ebx
            //   5d                   | pop                 ebp
            //   c3                   | ret                 
            //   8b7304               | mov                 esi, dword ptr [ebx + 4]
            //   31c0                 | xor                 eax, eax
            //   83fe18               | cmp                 esi, 0x18
            //   72ee                 | jb                  0xfffffff0

        $sequence_8 = { 8b0e 6a00 ff750c ff7508 51 ff15???????? 85c0 }
            // n = 7, score = 1100
            //   8b0e                 | mov                 ecx, dword ptr [esi]
            //   6a00                 | push                0
            //   ff750c               | push                dword ptr [ebp + 0xc]
            //   ff7508               | push                dword ptr [ebp + 8]
            //   51                   | push                ecx
            //   ff15????????         |                     
            //   85c0                 | test                eax, eax

        $sequence_9 = { 7509 ff7654 ff15???????? 807e5000 7509 ff764c ff15???????? }
            // n = 7, score = 1000
            //   7509                 | jne                 0xb
            //   ff7654               | push                dword ptr [esi + 0x54]
            //   ff15????????         |                     
            //   807e5000             | cmp                 byte ptr [esi + 0x50], 0
            //   7509                 | jne                 0xb
            //   ff764c               | push                dword ptr [esi + 0x4c]
            //   ff15????????         |                     

        $sequence_10 = { 895e0c 8b03 894604 83e880 }
            // n = 4, score = 1000
            //   895e0c               | mov                 dword ptr [esi + 0xc], ebx
            //   8b03                 | mov                 eax, dword ptr [ebx]
            //   894604               | mov                 dword ptr [esi + 4], eax
            //   83e880               | sub                 eax, -0x80

        $sequence_11 = { eb10 6800800000 6a00 56 }
            // n = 4, score = 1000
            //   eb10                 | jmp                 0x12
            //   6800800000           | push                0x8000
            //   6a00                 | push                0
            //   56                   | push                esi

        $sequence_12 = { 53 6800001040 6a03 53 53 68000000c0 }
            // n = 6, score = 1000
            //   53                   | push                ebx
            //   6800001040           | push                0x40100000
            //   6a03                 | push                3
            //   53                   | push                ebx
            //   53                   | push                ebx
            //   68000000c0           | push                0xc0000000

        $sequence_13 = { ff742428 e8???????? 8b442424 8d4c2410 }
            // n = 4, score = 1000
            //   ff742428             | push                dword ptr [esp + 0x28]
            //   e8????????           |                     
            //   8b442424             | mov                 eax, dword ptr [esp + 0x24]
            //   8d4c2410             | lea                 ecx, [esp + 0x10]

        $sequence_14 = { 8d4634 50 ff15???????? 8d4e0c }
            // n = 4, score = 1000
            //   8d4634               | lea                 eax, [esi + 0x34]
            //   50                   | push                eax
            //   ff15????????         |                     
            //   8d4e0c               | lea                 ecx, [esi + 0xc]

        $sequence_15 = { ff7010 ff7014 e8???????? 8b45e0 }
            // n = 4, score = 1000
            //   ff7010               | push                dword ptr [eax + 0x10]
            //   ff7014               | push                dword ptr [eax + 0x14]
            //   e8????????           |                     
            //   8b45e0               | mov                 eax, dword ptr [ebp - 0x20]

    condition:
        7 of them and filesize < 1302528
}
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