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 (20220808 | Detects win.grabbot.)
rule win_grabbot_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-08-05"
        version = "1"
        description = "Detects win.grabbot."
        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.grabbot"
        malpedia_rule_date = "20220805"
        malpedia_hash = "6ec06c64bcfdbeda64eff021c766b4ce34542b71"
        malpedia_version = "20220808"
        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 = { 83f841 7206 83c020 0fb7c0 }
            // n = 4, score = 3300
            //   83f841               | cmp                 eax, 0x41
            //   7206                 | jb                  8
            //   83c020               | add                 eax, 0x20
            //   0fb7c0               | movzx               eax, ax

        $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 = { ffd0 c20400 b8ff1f7cc9 50 e8???????? 50 }
            // n = 6, score = 3200
            //   ffd0                 | call                eax
            //   c20400               | ret                 4
            //   b8ff1f7cc9           | mov                 eax, 0xc97c1fff
            //   50                   | push                eax
            //   e8????????           |                     
            //   50                   | push                eax

        $sequence_4 = { 8d7008 50 66ad 85d2 741b 6685c0 7411 }
            // n = 7, score = 3200
            //   8d7008               | lea                 esi, [eax + 8]
            //   50                   | push                eax
            //   66ad                 | lodsw               ax, word ptr [esi]
            //   85d2                 | test                edx, edx
            //   741b                 | je                  0x1d
            //   6685c0               | test                ax, ax
            //   7411                 | je                  0x13

        $sequence_5 = { 682f6f0610 e8???????? 50 e8???????? ff7514 }
            // n = 5, score = 3200
            //   682f6f0610           | push                0x10066f2f
            //   e8????????           |                     
            //   50                   | push                eax
            //   e8????????           |                     
            //   ff7514               | push                dword ptr [ebp + 0x14]

        $sequence_6 = { 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_7 = { 33c0 5b 8be5 5d c3 8b4210 5f }
            // n = 7, score = 3200
            //   33c0                 | xor                 eax, eax
            //   5b                   | pop                 ebx
            //   8be5                 | mov                 esp, ebp
            //   5d                   | pop                 ebp
            //   c3                   | ret                 
            //   8b4210               | mov                 eax, dword ptr [edx + 0x10]
            //   5f                   | pop                 edi

        $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 = { 8b0d???????? 89480c e9???????? 33c0 e9???????? }
            // n = 5, score = 2300
            //   8b0d????????         |                     
            //   89480c               | mov                 dword ptr [eax + 0xc], ecx
            //   e9????????           |                     
            //   33c0                 | xor                 eax, eax
            //   e9????????           |                     

        $sequence_11 = { 50 e8???????? 56 e8???????? 83c414 8b4508 }
            // n = 6, score = 2000
            //   50                   | push                eax
            //   e8????????           |                     
            //   56                   | push                esi
            //   e8????????           |                     
            //   83c414               | add                 esp, 0x14
            //   8b4508               | mov                 eax, dword ptr [ebp + 8]

        $sequence_12 = { 6a00 6840420f00 6a00 ff15???????? a3???????? }
            // n = 5, score = 2000
            //   6a00                 | push                0
            //   6840420f00           | push                0xf4240
            //   6a00                 | push                0
            //   ff15????????         |                     
            //   a3????????           |                     

        $sequence_13 = { 741e 57 56 6aff }
            // n = 4, score = 2000
            //   741e                 | je                  0x20
            //   57                   | push                edi
            //   56                   | push                esi
            //   6aff                 | push                -1

        $sequence_14 = { 0f9fc3 e8???????? 83c414 5e }
            // n = 4, score = 2000
            //   0f9fc3               | setg                bl
            //   e8????????           |                     
            //   83c414               | add                 esp, 0x14
            //   5e                   | pop                 esi

        $sequence_15 = { 57 8d7c000c 57 e8???????? }
            // n = 4, score = 2000
            //   57                   | push                edi
            //   8d7c000c             | lea                 edi, [eax + eax + 0xc]
            //   57                   | push                edi
            //   e8????????           |                     

    condition:
        7 of them and filesize < 1335296
}
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