SYMBOLCOMMON_NAMEaka. SYNONYMS
win.grillmark (Back to overview)

GRILLMARK

aka: Hellsing Backdoor

Actor(s): Hellsing, Leviathan


This is a proxy-aware HTTP backdoor that is implemented as a service and uses the compromised system's proxy settings to access the internet. C&C traffic is base64 encoded and the files sent to the server are compressed with aPLib.

References
2019-04-11FireEyeFireEye
@online{fireeye:20190411:mtrend:597b240, author = {FireEye}, title = {{M-Trend 2019}}, date = {2019-04-11}, organization = {FireEye}, url = {https://content.fireeye.com/m-trends/rpt-m-trends-2019}, language = {English}, urldate = {2020-01-10} } M-Trend 2019
GRILLMARK
2015-04-15Kaspersky LabsCostin Raiu, Maxim Golovkin
@online{raiu:20150415:chronicles:aa4af84, author = {Costin Raiu and Maxim Golovkin}, title = {{The Chronicles of the Hellsing APT: the Empire Strikes Back}}, date = {2015-04-15}, organization = {Kaspersky Labs}, url = {https://securelist.com/the-chronicles-of-the-hellsing-apt-the-empire-strikes-back/69567/}, language = {English}, urldate = {2021-02-06} } The Chronicles of the Hellsing APT: the Empire Strikes Back
GRILLMARK Naikon
Yara Rules
[TLP:WHITE] win_grillmark_auto (20220411 | Detects win.grillmark.)
rule win_grillmark_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        version = "1"
        description = "Detects win.grillmark."
        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.grillmark"
        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 = { 53 50 6803000080 e8???????? 85c0 7404 33c0 }
            // n = 7, score = 300
            //   53                   | push                ebx
            //   50                   | push                eax
            //   6803000080           | push                0x80000003
            //   e8????????           |                     
            //   85c0                 | test                eax, eax
            //   7404                 | je                  6
            //   33c0                 | xor                 eax, eax

        $sequence_1 = { 66ab aa 895df8 c745fc20000000 c745f030750000 }
            // n = 5, score = 300
            //   66ab                 | stosw               word ptr es:[edi], ax
            //   aa                   | stosb               byte ptr es:[edi], al
            //   895df8               | mov                 dword ptr [ebp - 8], ebx
            //   c745fc20000000       | mov                 dword ptr [ebp - 4], 0x20
            //   c745f030750000       | mov                 dword ptr [ebp - 0x10], 0x7530

        $sequence_2 = { eb6c ff45f8 880f 47 eb64 80f909 7c43 }
            // n = 7, score = 300
            //   eb6c                 | jmp                 0x6e
            //   ff45f8               | inc                 dword ptr [ebp - 8]
            //   880f                 | mov                 byte ptr [edi], cl
            //   47                   | inc                 edi
            //   eb64                 | jmp                 0x66
            //   80f909               | cmp                 cl, 9
            //   7c43                 | jl                  0x45

        $sequence_3 = { 68???????? ff35???????? 56 e8???????? 68???????? ff75ec e8???????? }
            // n = 7, score = 300
            //   68????????           |                     
            //   ff35????????         |                     
            //   56                   | push                esi
            //   e8????????           |                     
            //   68????????           |                     
            //   ff75ec               | push                dword ptr [ebp - 0x14]
            //   e8????????           |                     

        $sequence_4 = { e8???????? 59 834dfcff e9???????? }
            // n = 4, score = 300
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   834dfcff             | or                  dword ptr [ebp - 4], 0xffffffff
            //   e9????????           |                     

        $sequence_5 = { 6a1a 50 53 ff15???????? 8d85fcfeffff 68???????? }
            // n = 6, score = 300
            //   6a1a                 | push                0x1a
            //   50                   | push                eax
            //   53                   | push                ebx
            //   ff15????????         |                     
            //   8d85fcfeffff         | lea                 eax, dword ptr [ebp - 0x104]
            //   68????????           |                     

        $sequence_6 = { 53 56 57 6a10 59 be???????? 8d7d84 }
            // n = 7, score = 300
            //   53                   | push                ebx
            //   56                   | push                esi
            //   57                   | push                edi
            //   6a10                 | push                0x10
            //   59                   | pop                 ecx
            //   be????????           |                     
            //   8d7d84               | lea                 edi, dword ptr [ebp - 0x7c]

        $sequence_7 = { 8d85f0feffff c745f404010000 50 c745f801000000 e8???????? 8d85f0feffff }
            // n = 6, score = 300
            //   8d85f0feffff         | lea                 eax, dword ptr [ebp - 0x110]
            //   c745f404010000       | mov                 dword ptr [ebp - 0xc], 0x104
            //   50                   | push                eax
            //   c745f801000000       | mov                 dword ptr [ebp - 8], 1
            //   e8????????           |                     
            //   8d85f0feffff         | lea                 eax, dword ptr [ebp - 0x110]

        $sequence_8 = { 8945fc 0f84b8000000 56 e8???????? }
            // n = 4, score = 300
            //   8945fc               | mov                 dword ptr [ebp - 4], eax
            //   0f84b8000000         | je                  0xbe
            //   56                   | push                esi
            //   e8????????           |                     

        $sequence_9 = { 59 85c0 59 0f85af020000 8b7df4 68???????? }
            // n = 6, score = 300
            //   59                   | pop                 ecx
            //   85c0                 | test                eax, eax
            //   59                   | pop                 ecx
            //   0f85af020000         | jne                 0x2b5
            //   8b7df4               | mov                 edi, dword ptr [ebp - 0xc]
            //   68????????           |                     

    condition:
        7 of them and filesize < 212992
}
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