SYMBOLCOMMON_NAMEaka. SYNONYMS
win.tclient (Back to overview)

TClient

aka: FIRESHADOW

Actor(s): Pirate Panda


Steve Miller pointed out that it is proxy-aware (Tencent) for C&C communication and uses wolfSSL, which makes it stick out.

References
2020-05-28Twitter (@stvemillertime)Steve Miller
@online{miller:20200528:tclient:cc952e5, author = {Steve Miller}, title = {{Tweet on TClient / FIRESHADOW used by Tropic Trooper}}, date = {2020-05-28}, organization = {Twitter (@stvemillertime)}, url = {https://twitter.com/stvemillertime/status/1266050369370677249}, language = {English}, urldate = {2020-06-05} } Tweet on TClient / FIRESHADOW used by Tropic Trooper
TClient
Yara Rules
[TLP:WHITE] win_tclient_auto (20220411 | Detects win.tclient.)
rule win_tclient_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        version = "1"
        description = "Detects win.tclient."
        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.tclient"
        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 = { 85c0 753b 8b4630 395844 7405 ff7044 ffd7 }
            // n = 7, score = 100
            //   85c0                 | test                eax, eax
            //   753b                 | jne                 0x3d
            //   8b4630               | mov                 eax, dword ptr [esi + 0x30]
            //   395844               | cmp                 dword ptr [eax + 0x44], ebx
            //   7405                 | je                  7
            //   ff7044               | push                dword ptr [eax + 0x44]
            //   ffd7                 | call                edi

        $sequence_1 = { 8b4b0c 8bd7 56 81c1a0020000 e8???????? 59 85c0 }
            // n = 7, score = 100
            //   8b4b0c               | mov                 ecx, dword ptr [ebx + 0xc]
            //   8bd7                 | mov                 edx, edi
            //   56                   | push                esi
            //   81c1a0020000         | add                 ecx, 0x2a0
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   85c0                 | test                eax, eax

        $sequence_2 = { 8b85d0feffff 3385d8feffff 23c3 3385d8feffff 03d0 8bcf 8b85c4feffff }
            // n = 7, score = 100
            //   8b85d0feffff         | mov                 eax, dword ptr [ebp - 0x130]
            //   3385d8feffff         | xor                 eax, dword ptr [ebp - 0x128]
            //   23c3                 | and                 eax, ebx
            //   3385d8feffff         | xor                 eax, dword ptr [ebp - 0x128]
            //   03d0                 | add                 edx, eax
            //   8bcf                 | mov                 ecx, edi
            //   8b85c4feffff         | mov                 eax, dword ptr [ebp - 0x13c]

        $sequence_3 = { 83e801 79f4 8bbd48ffffff 6a37 5e 47 89bd48ffffff }
            // n = 7, score = 100
            //   83e801               | sub                 eax, 1
            //   79f4                 | jns                 0xfffffff6
            //   8bbd48ffffff         | mov                 edi, dword ptr [ebp - 0xb8]
            //   6a37                 | push                0x37
            //   5e                   | pop                 esi
            //   47                   | inc                 edi
            //   89bd48ffffff         | mov                 dword ptr [ebp - 0xb8], edi

        $sequence_4 = { 8955e0 85db 0f8433020000 397dbc 0f842a020000 8b4510 0fb696f9010000 }
            // n = 7, score = 100
            //   8955e0               | mov                 dword ptr [ebp - 0x20], edx
            //   85db                 | test                ebx, ebx
            //   0f8433020000         | je                  0x239
            //   397dbc               | cmp                 dword ptr [ebp - 0x44], edi
            //   0f842a020000         | je                  0x230
            //   8b4510               | mov                 eax, dword ptr [ebp + 0x10]
            //   0fb696f9010000       | movzx               edx, byte ptr [esi + 0x1f9]

        $sequence_5 = { 50 e8???????? 83c424 8b95fcfdffff 8bc2 d1e8 2401 }
            // n = 7, score = 100
            //   50                   | push                eax
            //   e8????????           |                     
            //   83c424               | add                 esp, 0x24
            //   8b95fcfdffff         | mov                 edx, dword ptr [ebp - 0x204]
            //   8bc2                 | mov                 eax, edx
            //   d1e8                 | shr                 eax, 1
            //   2401                 | and                 al, 1

        $sequence_6 = { 59 85c0 0f859b000000 6a30 8d96e0010000 8bce e8???????? }
            // n = 7, score = 100
            //   59                   | pop                 ecx
            //   85c0                 | test                eax, eax
            //   0f859b000000         | jne                 0xa1
            //   6a30                 | push                0x30
            //   8d96e0010000         | lea                 edx, dword ptr [esi + 0x1e0]
            //   8bce                 | mov                 ecx, esi
            //   e8????????           |                     

        $sequence_7 = { 23048d30a94600 8b4df4 03d0 e8???????? 8bf0 85f6 0f85c2000000 }
            // n = 7, score = 100
            //   23048d30a94600       | and                 eax, dword ptr [ecx*4 + 0x46a930]
            //   8b4df4               | mov                 ecx, dword ptr [ebp - 0xc]
            //   03d0                 | add                 edx, eax
            //   e8????????           |                     
            //   8bf0                 | mov                 esi, eax
            //   85f6                 | test                esi, esi
            //   0f85c2000000         | jne                 0xc8

        $sequence_8 = { 807d0803 750c c1eb08 80fb03 7204 8bc6 eb02 }
            // n = 7, score = 100
            //   807d0803             | cmp                 byte ptr [ebp + 8], 3
            //   750c                 | jne                 0xe
            //   c1eb08               | shr                 ebx, 8
            //   80fb03               | cmp                 bl, 3
            //   7204                 | jb                  6
            //   8bc6                 | mov                 eax, esi
            //   eb02                 | jmp                 4

        $sequence_9 = { 42 e8???????? 83c410 57 6a01 8d4d08 e8???????? }
            // n = 7, score = 100
            //   42                   | inc                 edx
            //   e8????????           |                     
            //   83c410               | add                 esp, 0x10
            //   57                   | push                edi
            //   6a01                 | push                1
            //   8d4d08               | lea                 ecx, dword ptr [ebp + 8]
            //   e8????????           |                     

    condition:
        7 of them and filesize < 1063936
}
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