SYMBOLCOMMON_NAMEaka. SYNONYMS
win.skinnyboy (Back to overview)

SkinnyBoy


There is no description at this point.

References
2021-08-03Cyber GeeksCyberMasterV
@online{cybermasterv:20210803:stepbystep:2c73656, author = {CyberMasterV}, title = {{A step-by-step analysis of the new malware used by APT28/Sofacy called SkinnyBoy}}, date = {2021-08-03}, organization = {Cyber Geeks}, url = {https://cybergeeks.tech/skinnyboy-apt28/}, language = {English}, urldate = {2021-08-06} } A step-by-step analysis of the new malware used by APT28/Sofacy called SkinnyBoy
SkinnyBoy
2021-05Cluster25Cluster25
@techreport{cluster25:202105:not:0bf7be8, author = {Cluster25}, title = {{A Not So Fancy Game: Exploring the New SkinnyBoy Bear's Backdoor}}, date = {2021-05}, institution = {Cluster25}, url = {https://cluster25.io/wp-content/uploads/2021/05/2021-05_FancyBear.pdf}, language = {English}, urldate = {2021-06-07} } A Not So Fancy Game: Exploring the New SkinnyBoy Bear's Backdoor
SkinnyBoy
Yara Rules
[TLP:WHITE] win_skinnyboy_auto (20221125 | Detects win.skinnyboy.)
rule win_skinnyboy_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-11-21"
        version = "1"
        description = "Detects win.skinnyboy."
        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.skinnyboy"
        malpedia_rule_date = "20221118"
        malpedia_hash = "e0702e2e6d1d00da65c8a29a4ebacd0a4c59e1af"
        malpedia_version = "20221125"
        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 = { 8945e4 0fb705???????? 668945e8 0f57c0 }
            // n = 4, score = 100
            //   8945e4               | mov                 dword ptr [ebp - 0x1c], eax
            //   0fb705????????       |                     
            //   668945e8             | mov                 word ptr [ebp - 0x18], ax
            //   0f57c0               | xorps               xmm0, xmm0

        $sequence_1 = { 8bd9 50 899554fbffff 899d60fbffff }
            // n = 4, score = 100
            //   8bd9                 | mov                 ebx, ecx
            //   50                   | push                eax
            //   899554fbffff         | mov                 dword ptr [ebp - 0x4ac], edx
            //   899d60fbffff         | mov                 dword ptr [ebp - 0x4a0], ebx

        $sequence_2 = { 8975fc 8b45e0 8b048510110110 f644030401 }
            // n = 4, score = 100
            //   8975fc               | mov                 dword ptr [ebp - 4], esi
            //   8b45e0               | mov                 eax, dword ptr [ebp - 0x20]
            //   8b048510110110       | mov                 eax, dword ptr [eax*4 + 0x10011110]
            //   f644030401           | test                byte ptr [ebx + eax + 4], 1

        $sequence_3 = { c745de00000000 66c745e20000 660fd645ea c745f200000000 66c745f60000 }
            // n = 5, score = 100
            //   c745de00000000       | mov                 dword ptr [ebp - 0x22], 0
            //   66c745e20000         | mov                 word ptr [ebp - 0x1e], 0
            //   660fd645ea           | movq                qword ptr [ebp - 0x16], xmm0
            //   c745f200000000       | mov                 dword ptr [ebp - 0xe], 0
            //   66c745f60000         | mov                 word ptr [ebp - 0xa], 0

        $sequence_4 = { 6a55 ff34f588d40010 ff7508 e8???????? 83c40c }
            // n = 5, score = 100
            //   6a55                 | push                0x55
            //   ff34f588d40010       | push                dword ptr [esi*8 + 0x1000d488]
            //   ff7508               | push                dword ptr [ebp + 8]
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc

        $sequence_5 = { 89442438 8b442430 89442440 8b44241c 89442444 8b442420 89742434 }
            // n = 7, score = 100
            //   89442438             | mov                 dword ptr [esp + 0x38], eax
            //   8b442430             | mov                 eax, dword ptr [esp + 0x30]
            //   89442440             | mov                 dword ptr [esp + 0x40], eax
            //   8b44241c             | mov                 eax, dword ptr [esp + 0x1c]
            //   89442444             | mov                 dword ptr [esp + 0x44], eax
            //   8b442420             | mov                 eax, dword ptr [esp + 0x20]
            //   89742434             | mov                 dword ptr [esp + 0x34], esi

        $sequence_6 = { 6af6 ff15???????? 8b04bd10110110 830c06ff 33c0 }
            // n = 5, score = 100
            //   6af6                 | push                -0xa
            //   ff15????????         |                     
            //   8b04bd10110110       | mov                 eax, dword ptr [edi*4 + 0x10011110]
            //   830c06ff             | or                  dword ptr [esi + eax], 0xffffffff
            //   33c0                 | xor                 eax, eax

        $sequence_7 = { c745f800000000 ff15???????? 8b35???????? 8d45f8 }
            // n = 4, score = 100
            //   c745f800000000       | mov                 dword ptr [ebp - 8], 0
            //   ff15????????         |                     
            //   8b35????????         |                     
            //   8d45f8               | lea                 eax, [ebp - 8]

        $sequence_8 = { 8b54240c 33c0 33db c744242000000000 }
            // n = 4, score = 100
            //   8b54240c             | mov                 edx, dword ptr [esp + 0xc]
            //   33c0                 | xor                 eax, eax
            //   33db                 | xor                 ebx, ebx
            //   c744242000000000     | mov                 dword ptr [esp + 0x20], 0

        $sequence_9 = { 6a00 6a01 51 03f7 56 898dccfeffff }
            // n = 6, score = 100
            //   6a00                 | push                0
            //   6a01                 | push                1
            //   51                   | push                ecx
            //   03f7                 | add                 esi, edi
            //   56                   | push                esi
            //   898dccfeffff         | mov                 dword ptr [ebp - 0x134], ecx

    condition:
        7 of them and filesize < 176128
}
Download all Yara Rules