SYMBOLCOMMON_NAMEaka. SYNONYMS
win.grabbot (Back to overview)

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References
2017-03-17FortinetDavid Wang, He Xu
@online{wang:20170317:grabbot:e8dde0d, author = {David Wang and He Xu}, title = {{Grabbot is Back to Nab Your Data}}, date = {2017-03-17}, organization = {Fortinet}, url = {http://blog.fortinet.com/2017/03/17/grabbot-is-back-to-nab-your-data}, language = {English}, urldate = {2020-01-06} } Grabbot is Back to Nab Your Data
GrabBot
Yara Rules
[TLP:WHITE] win_grabbot_auto (20201023 | autogenerated rule brought to you by yara-signator)
rule win_grabbot_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2020-12-22"
        version = "1"
        description = "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.grabbot"
        malpedia_rule_date = "20201222"
        malpedia_hash = "30354d830a29f0fbd3714d93d94dea941d77a130"
        malpedia_version = "20201023"
        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 = { 0fb702 83f85a 770b 83f841 }
            // n = 4, score = 3300
            //   0fb702               | movzx               eax, word ptr [edx]
            //   83f85a               | cmp                 eax, 0x5a
            //   770b                 | ja                  0xd
            //   83f841               | cmp                 eax, 0x41

        $sequence_1 = { 770b 83f841 7206 83c020 0fb7c0 83c202 }
            // n = 6, score = 3300
            //   770b                 | ja                  0xd
            //   83f841               | cmp                 eax, 0x41
            //   7206                 | jb                  8
            //   83c020               | add                 eax, 0x20
            //   0fb7c0               | movzx               eax, ax
            //   83c202               | add                 edx, 2

        $sequence_2 = { 770d 83f841 7208 83c020 }
            // n = 4, score = 3300
            //   770d                 | ja                  0xf
            //   83f841               | cmp                 eax, 0x41
            //   7208                 | jb                  0xa
            //   83c020               | add                 eax, 0x20

        $sequence_3 = { 6a04 52 e8???????? 5a 85c0 0f859a000000 8bfa }
            // n = 7, score = 3200
            //   6a04                 | push                4
            //   52                   | push                edx
            //   e8????????           |                     
            //   5a                   | pop                 edx
            //   85c0                 | test                eax, eax
            //   0f859a000000         | jne                 0xa0
            //   8bfa                 | mov                 edi, edx

        $sequence_4 = { e8???????? 50 e8???????? ffe0 c3 68d0035c09 e8???????? }
            // n = 7, score = 3200
            //   e8????????           |                     
            //   50                   | push                eax
            //   e8????????           |                     
            //   ffe0                 | jmp                 eax
            //   c3                   | ret                 
            //   68d0035c09           | push                0x95c03d0
            //   e8????????           |                     

        $sequence_5 = { 8b80c0000000 85c0 7424 03c3 8b5d34 }
            // n = 5, score = 3200
            //   8b80c0000000         | mov                 eax, dword ptr [eax + 0xc0]
            //   85c0                 | test                eax, eax
            //   7424                 | je                  0x26
            //   03c3                 | add                 eax, ebx
            //   8b5d34               | mov                 ebx, dword ptr [ebp + 0x34]

        $sequence_6 = { 03ca 3bc1 773f 81ec80000000 8bdc 53 }
            // n = 6, score = 3200
            //   03ca                 | add                 ecx, edx
            //   3bc1                 | cmp                 eax, ecx
            //   773f                 | ja                  0x41
            //   81ec80000000         | sub                 esp, 0x80
            //   8bdc                 | mov                 ebx, esp
            //   53                   | push                ebx

        $sequence_7 = { 85c0 0f88b6000000 8b55fc 85d2 0f84ab000000 8b33 }
            // n = 6, score = 3200
            //   85c0                 | test                eax, eax
            //   0f88b6000000         | js                  0xbc
            //   8b55fc               | mov                 edx, dword ptr [ebp - 4]
            //   85d2                 | test                edx, edx
            //   0f84ab000000         | je                  0xb1
            //   8b33                 | mov                 esi, dword ptr [ebx]

        $sequence_8 = { 56 ffd0 33c9 66894c37fe }
            // n = 4, score = 2600
            //   56                   | push                esi
            //   ffd0                 | call                eax
            //   33c9                 | xor                 ecx, ecx
            //   66894c37fe           | mov                 word ptr [edi + esi - 2], cx

        $sequence_9 = { 7428 8b0d???????? 8908 8b0d???????? 894804 }
            // n = 5, score = 2300
            //   7428                 | je                  0x2a
            //   8b0d????????         |                     
            //   8908                 | mov                 dword ptr [eax], ecx
            //   8b0d????????         |                     
            //   894804               | mov                 dword ptr [eax + 4], ecx

        $sequence_10 = { 89480c e9???????? 33c0 e9???????? }
            // n = 4, score = 2300
            //   89480c               | mov                 dword ptr [eax + 0xc], ecx
            //   e9????????           |                     
            //   33c0                 | xor                 eax, eax
            //   e9????????           |                     

        $sequence_11 = { 8b0d???????? 894804 8b0d???????? 894808 8b0d???????? 89480c e9???????? }
            // n = 7, score = 2300
            //   8b0d????????         |                     
            //   894804               | mov                 dword ptr [eax + 4], ecx
            //   8b0d????????         |                     
            //   894808               | mov                 dword ptr [eax + 8], ecx
            //   8b0d????????         |                     
            //   89480c               | mov                 dword ptr [eax + 0xc], ecx
            //   e9????????           |                     

        $sequence_12 = { ff15???????? 50 ff15???????? a3???????? 85c0 7505 83c8ff }
            // n = 7, score = 2000
            //   ff15????????         |                     
            //   50                   | push                eax
            //   ff15????????         |                     
            //   a3????????           |                     
            //   85c0                 | test                eax, eax
            //   7505                 | jne                 7
            //   83c8ff               | or                  eax, 0xffffffff

        $sequence_13 = { 85c0 56 0f9fc3 e8???????? 83c414 5e 8ac3 }
            // n = 7, score = 2000
            //   85c0                 | test                eax, eax
            //   56                   | push                esi
            //   0f9fc3               | setg                bl
            //   e8????????           |                     
            //   83c414               | add                 esp, 0x14
            //   5e                   | pop                 esi
            //   8ac3                 | mov                 al, bl

        $sequence_14 = { ff15???????? 85c0 741b 8d440002 50 e8???????? }
            // n = 6, score = 2000
            //   ff15????????         |                     
            //   85c0                 | test                eax, eax
            //   741b                 | je                  0x1d
            //   8d440002             | lea                 eax, [eax + eax + 2]
            //   50                   | push                eax
            //   e8????????           |                     

        $sequence_15 = { 33ff 85f6 7405 83feff }
            // n = 4, score = 2000
            //   33ff                 | xor                 edi, edi
            //   85f6                 | test                esi, esi
            //   7405                 | je                  7
            //   83feff               | cmp                 esi, -1

    condition:
        7 of them and filesize < 1335296
}
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