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 (20220516 | Detects win.skinnyboy.)
rule win_skinnyboy_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-05-16"
        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 = "20220513"
        malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26"
        malpedia_version = "20220516"
        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 = { ff15???????? ff742414 8bf8 8b442410 03c3 83c608 03c6 }
            // n = 7, score = 100
            //   ff15????????         |                     
            //   ff742414             | push                dword ptr [esp + 0x14]
            //   8bf8                 | mov                 edi, eax
            //   8b442410             | mov                 eax, dword ptr [esp + 0x10]
            //   03c3                 | add                 eax, ebx
            //   83c608               | add                 esi, 8
            //   03c6                 | add                 eax, esi

        $sequence_1 = { 8d8560fdffff 50 8d8558fbffff 50 }
            // n = 4, score = 100
            //   8d8560fdffff         | lea                 eax, [ebp - 0x2a0]
            //   50                   | push                eax
            //   8d8558fbffff         | lea                 eax, [ebp - 0x4a8]
            //   50                   | push                eax

        $sequence_2 = { 8d442410 50 8d542410 c744241000000000 c744241400000000 e8???????? 8b4c2414 }
            // n = 7, score = 100
            //   8d442410             | lea                 eax, [esp + 0x10]
            //   50                   | push                eax
            //   8d542410             | lea                 edx, [esp + 0x10]
            //   c744241000000000     | mov                 dword ptr [esp + 0x10], 0
            //   c744241400000000     | mov                 dword ptr [esp + 0x14], 0
            //   e8????????           |                     
            //   8b4c2414             | mov                 ecx, dword ptr [esp + 0x14]

        $sequence_3 = { 8bc1 c1f805 c1e206 03148510110110 83c8ff eb02 }
            // n = 6, score = 100
            //   8bc1                 | mov                 eax, ecx
            //   c1f805               | sar                 eax, 5
            //   c1e206               | shl                 edx, 6
            //   03148510110110       | add                 edx, dword ptr [eax*4 + 0x10011110]
            //   83c8ff               | or                  eax, 0xffffffff
            //   eb02                 | jmp                 4

        $sequence_4 = { ffb5ec6ffeff 8b35???????? ffd6 ffb5f06ffeff ffd6 }
            // n = 5, score = 100
            //   ffb5ec6ffeff         | push                dword ptr [ebp - 0x19014]
            //   8b35????????         |                     
            //   ffd6                 | call                esi
            //   ffb5f06ffeff         | push                dword ptr [ebp - 0x19010]
            //   ffd6                 | call                esi

        $sequence_5 = { 660fd645e5 c645ed00 e8???????? 6a5b }
            // n = 4, score = 100
            //   660fd645e5           | movq                qword ptr [ebp - 0x1b], xmm0
            //   c645ed00             | mov                 byte ptr [ebp - 0x13], 0
            //   e8????????           |                     
            //   6a5b                 | push                0x5b

        $sequence_6 = { 8bce 894de0 83f905 7d10 668b444b0c 6689044d2c130110 }
            // n = 6, score = 100
            //   8bce                 | mov                 ecx, esi
            //   894de0               | mov                 dword ptr [ebp - 0x20], ecx
            //   83f905               | cmp                 ecx, 5
            //   7d10                 | jge                 0x12
            //   668b444b0c           | mov                 ax, word ptr [ebx + ecx*2 + 0xc]
            //   6689044d2c130110     | mov                 word ptr [ecx*2 + 0x1001132c], ax

        $sequence_7 = { 85c0 0f8487000000 8b15???????? 56 8b75f4 85f6 }
            // n = 6, score = 100
            //   85c0                 | test                eax, eax
            //   0f8487000000         | je                  0x8d
            //   8b15????????         |                     
            //   56                   | push                esi
            //   8b75f4               | mov                 esi, dword ptr [ebp - 0xc]
            //   85f6                 | test                esi, esi

        $sequence_8 = { c1f805 83e71f c1e706 8b048510110110 83c00c 03c7 50 }
            // n = 7, score = 100
            //   c1f805               | sar                 eax, 5
            //   83e71f               | and                 edi, 0x1f
            //   c1e706               | shl                 edi, 6
            //   8b048510110110       | mov                 eax, dword ptr [eax*4 + 0x10011110]
            //   83c00c               | add                 eax, 0xc
            //   03c7                 | add                 eax, edi
            //   50                   | push                eax

        $sequence_9 = { 50 eb20 8b07 03c6 50 51 }
            // n = 6, score = 100
            //   50                   | push                eax
            //   eb20                 | jmp                 0x22
            //   8b07                 | mov                 eax, dword ptr [edi]
            //   03c6                 | add                 eax, esi
            //   50                   | push                eax
            //   51                   | push                ecx

    condition:
        7 of them and filesize < 176128
}
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