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 (20200817 | autogenerated rule brought to you by yara-signator)
rule win_grabbot_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2020-08-17"
        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.grabbot"
        malpedia_rule_date = "20200817"
        malpedia_hash = "8c895fd01eccb47a6225bcb1a3ba53cbb98644c5"
        malpedia_version = "20200817"
        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 = { 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_1 = { 83f85a 770d 83f841 7208 83c020 }
            // n = 5, score = 3300
            //   83f85a               | cmp                 eax, 0x5a
            //   770d                 | ja                  0xf
            //   83f841               | cmp                 eax, 0x41
            //   7208                 | jb                  0xa
            //   83c020               | add                 eax, 0x20

        $sequence_2 = { 8b18 8b5004 83ea08 8d7008 50 }
            // n = 5, score = 3200
            //   8b18                 | mov                 ebx, dword ptr [eax]
            //   8b5004               | mov                 edx, dword ptr [eax + 4]
            //   83ea08               | sub                 edx, 8
            //   8d7008               | lea                 esi, [eax + 8]
            //   50                   | push                eax

        $sequence_3 = { c745c06f636564 c745c475726541 c745c864647265 66c745cc7373 c645ce00 }
            // n = 5, score = 3200
            //   c745c06f636564       | mov                 dword ptr [ebp - 0x40], 0x6465636f
            //   c745c475726541       | mov                 dword ptr [ebp - 0x3c], 0x41657275
            //   c745c864647265       | mov                 dword ptr [ebp - 0x38], 0x65726464
            //   66c745cc7373         | mov                 word ptr [ebp - 0x34], 0x7373
            //   c645ce00             | mov                 byte ptr [ebp - 0x32], 0

        $sequence_4 = { 8b4830 8b7834 bb4c010000 663bd3 7505 }
            // n = 5, score = 3200
            //   8b4830               | mov                 ecx, dword ptr [eax + 0x30]
            //   8b7834               | mov                 edi, dword ptr [eax + 0x34]
            //   bb4c010000           | mov                 ebx, 0x14c
            //   663bd3               | cmp                 dx, bx
            //   7505                 | jne                 7

        $sequence_5 = { ffe0 c3 68a0f7bf08 e8???????? 50 }
            // n = 5, score = 3200
            //   ffe0                 | jmp                 eax
            //   c3                   | ret                 
            //   68a0f7bf08           | push                0x8bff7a0
            //   e8????????           |                     
            //   50                   | push                eax

        $sequence_6 = { 0f84ac000000 52 6a04 52 e8???????? 5a 85c0 }
            // n = 7, score = 3200
            //   0f84ac000000         | je                  0xb2
            //   52                   | push                edx
            //   6a04                 | push                4
            //   52                   | push                edx
            //   e8????????           |                     
            //   5a                   | pop                 edx
            //   85c0                 | test                eax, eax

        $sequence_7 = { 85f6 7409 8b84c88c000000 8906 8d043a }
            // n = 5, score = 3200
            //   85f6                 | test                esi, esi
            //   7409                 | je                  0xb
            //   8b84c88c000000       | mov                 eax, dword ptr [eax + ecx*8 + 0x8c]
            //   8906                 | mov                 dword ptr [esi], eax
            //   8d043a               | lea                 eax, [edx + edi]

        $sequence_8 = { 56 ffd0 33c9 66894c37fe }
            // n = 4, score = 2300
            //   56                   | push                esi
            //   ffd0                 | call                eax
            //   33c9                 | xor                 ecx, ecx
            //   66894c37fe           | mov                 word ptr [edi + esi - 2], cx

        $sequence_9 = { 894808 8b0d???????? 89480c e9???????? 33c0 e9???????? }
            // n = 6, score = 2000
            //   894808               | mov                 dword ptr [eax + 8], ecx
            //   8b0d????????         |                     
            //   89480c               | mov                 dword ptr [eax + 0xc], ecx
            //   e9????????           |                     
            //   33c0                 | xor                 eax, eax
            //   e9????????           |                     

        $sequence_10 = { 7428 8b0d???????? 8908 8b0d???????? }
            // n = 4, score = 2000
            //   7428                 | je                  0x2a
            //   8b0d????????         |                     
            //   8908                 | mov                 dword ptr [eax], ecx
            //   8b0d????????         |                     

        $sequence_11 = { 8d45f0 99 52 50 8b451c 99 52 }
            // n = 7, score = 1700
            //   8d45f0               | lea                 eax, [ebp - 0x10]
            //   99                   | cdq                 
            //   52                   | push                edx
            //   50                   | push                eax
            //   8b451c               | mov                 eax, dword ptr [ebp + 0x1c]
            //   99                   | cdq                 
            //   52                   | push                edx

        $sequence_12 = { 6a00 6840420f00 6a00 ff15???????? a3???????? 85c0 }
            // n = 6, score = 1700
            //   6a00                 | push                0
            //   6840420f00           | push                0xf4240
            //   6a00                 | push                0
            //   ff15????????         |                     
            //   a3????????           |                     
            //   85c0                 | test                eax, eax

        $sequence_13 = { 85c0 741b 8d440002 50 e8???????? }
            // n = 5, score = 1700
            //   85c0                 | test                eax, eax
            //   741b                 | je                  0x1d
            //   8d440002             | lea                 eax, [eax + eax + 2]
            //   50                   | push                eax
            //   e8????????           |                     

    condition:
        7 of them and filesize < 1335296
}
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