SYMBOLCOMMON_NAMEaka. SYNONYMS
win.rarstar (Back to overview)

rarstar

Actor(s): Tick


There is no description at this point.

References
2017-10-12SecureworksCTU Research Team
@online{team:20171012:bronze:7b9ae02, author = {CTU Research Team}, title = {{BRONZE BUTLER Targets Japanese Enterprises}}, date = {2017-10-12}, organization = {Secureworks}, url = {https://www.secureworks.com/research/bronze-butler-targets-japanese-businesses}, language = {English}, urldate = {2020-01-07} } BRONZE BUTLER Targets Japanese Enterprises
Daserf Datper rarstar xxmm Tick
Yara Rules
[TLP:WHITE] win_rarstar_auto (20220411 | Detects win.rarstar.)
rule win_rarstar_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        version = "1"
        description = "Detects win.rarstar."
        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.rarstar"
        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 = { 745f 50 c705????????01000000 e8???????? }
            // n = 4, score = 100
            //   745f                 | je                  0x61
            //   50                   | push                eax
            //   c705????????01000000     |     
            //   e8????????           |                     

        $sequence_1 = { 83c40c 48 89442414 0f8544ffffff 8b4c2418 51 e8???????? }
            // n = 7, score = 100
            //   83c40c               | add                 esp, 0xc
            //   48                   | dec                 eax
            //   89442414             | mov                 dword ptr [esp + 0x14], eax
            //   0f8544ffffff         | jne                 0xffffff4a
            //   8b4c2418             | mov                 ecx, dword ptr [esp + 0x18]
            //   51                   | push                ecx
            //   e8????????           |                     

        $sequence_2 = { 8d6afe 33ff 8bc1 85ed 7e6f }
            // n = 5, score = 100
            //   8d6afe               | lea                 ebp, dword ptr [edx - 2]
            //   33ff                 | xor                 edi, edi
            //   8bc1                 | mov                 eax, ecx
            //   85ed                 | test                ebp, ebp
            //   7e6f                 | jle                 0x71

        $sequence_3 = { 56 57 b940000000 33c0 8d7c2420 c744241c74924000 }
            // n = 6, score = 100
            //   56                   | push                esi
            //   57                   | push                edi
            //   b940000000           | mov                 ecx, 0x40
            //   33c0                 | xor                 eax, eax
            //   8d7c2420             | lea                 edi, dword ptr [esp + 0x20]
            //   c744241c74924000     | mov                 dword ptr [esp + 0x1c], 0x409274

        $sequence_4 = { ff15???????? 8b3d???????? 8d942424040000 52 ffd7 8d84241c020000 }
            // n = 6, score = 100
            //   ff15????????         |                     
            //   8b3d????????         |                     
            //   8d942424040000       | lea                 edx, dword ptr [esp + 0x424]
            //   52                   | push                edx
            //   ffd7                 | call                edi
            //   8d84241c020000       | lea                 eax, dword ptr [esp + 0x21c]

        $sequence_5 = { 81ce00ffffff 46 89b42424030000 8a10 8d743420 }
            // n = 5, score = 100
            //   81ce00ffffff         | or                  esi, 0xffffff00
            //   46                   | inc                 esi
            //   89b42424030000       | mov                 dword ptr [esp + 0x324], esi
            //   8a10                 | mov                 dl, byte ptr [eax]
            //   8d743420             | lea                 esi, dword ptr [esp + esi + 0x20]

        $sequence_6 = { 50 68???????? 57 895c241c }
            // n = 4, score = 100
            //   50                   | push                eax
            //   68????????           |                     
            //   57                   | push                edi
            //   895c241c             | mov                 dword ptr [esp + 0x1c], ebx

        $sequence_7 = { f3ab bf???????? 83c9ff 33db 8d942424020000 }
            // n = 5, score = 100
            //   f3ab                 | rep stosd           dword ptr es:[edi], eax
            //   bf????????           |                     
            //   83c9ff               | or                  ecx, 0xffffffff
            //   33db                 | xor                 ebx, ebx
            //   8d942424020000       | lea                 edx, dword ptr [esp + 0x224]

        $sequence_8 = { ffd6 8b442418 83ceff 3bc6 7403 56 ffd7 }
            // n = 7, score = 100
            //   ffd6                 | call                esi
            //   8b442418             | mov                 eax, dword ptr [esp + 0x18]
            //   83ceff               | or                  esi, 0xffffffff
            //   3bc6                 | cmp                 eax, esi
            //   7403                 | je                  5
            //   56                   | push                esi
            //   ffd7                 | call                edi

        $sequence_9 = { 8d4c2424 51 8d942484000000 6800100000 52 50 ffd5 }
            // n = 7, score = 100
            //   8d4c2424             | lea                 ecx, dword ptr [esp + 0x24]
            //   51                   | push                ecx
            //   8d942484000000       | lea                 edx, dword ptr [esp + 0x84]
            //   6800100000           | push                0x1000
            //   52                   | push                edx
            //   50                   | push                eax
            //   ffd5                 | call                ebp

    condition:
        7 of them and filesize < 122880
}
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