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.
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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