Actor(s): Pirate Panda
PcShare is a open-source backdoor which has been seen modified and used by Chinese threat actors, mainly attacking countries in South East Asia.
rule win_pcshare_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.pcshare." 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.pcshare" malpedia_rule_date = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" 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 = { f60001 0f85a0000000 8d4dc4 6a01 51 e8???????? 8bf0 } // n = 7, score = 100 // f60001 | test byte ptr [eax], 1 // 0f85a0000000 | jne 0xa6 // 8d4dc4 | lea ecx, [ebp - 0x3c] // 6a01 | push 1 // 51 | push ecx // e8???????? | // 8bf0 | mov esi, eax $sequence_1 = { e8???????? 8d86e4020000 50 e8???????? 81c628040000 56 e8???????? } // n = 7, score = 100 // e8???????? | // 8d86e4020000 | lea eax, [esi + 0x2e4] // 50 | push eax // e8???????? | // 81c628040000 | add esi, 0x428 // 56 | push esi // e8???????? | $sequence_2 = { e8???????? 83c40c 85c0 7c23 03d8 56 8b75fc } // n = 7, score = 100 // e8???????? | // 83c40c | add esp, 0xc // 85c0 | test eax, eax // 7c23 | jl 0x25 // 03d8 | add ebx, eax // 56 | push esi // 8b75fc | mov esi, dword ptr [ebp - 4] $sequence_3 = { c1e707 0bdf 8b7df8 33f3 8b5df4 33f9 23fb } // n = 7, score = 100 // c1e707 | shl edi, 7 // 0bdf | or ebx, edi // 8b7df8 | mov edi, dword ptr [ebp - 8] // 33f3 | xor esi, ebx // 8b5df4 | mov ebx, dword ptr [ebp - 0xc] // 33f9 | xor edi, ecx // 23fb | and edi, ebx $sequence_4 = { e8???????? 8bf0 83c408 85f6 0f85bc020000 8b55f0 f60201 } // n = 7, score = 100 // e8???????? | // 8bf0 | mov esi, eax // 83c408 | add esp, 8 // 85f6 | test esi, esi // 0f85bc020000 | jne 0x2c2 // 8b55f0 | mov edx, dword ptr [ebp - 0x10] // f60201 | test byte ptr [edx], 1 $sequence_5 = { 51 56 e8???????? 83c40c 85c0 755d 8b435c } // n = 7, score = 100 // 51 | push ecx // 56 | push esi // e8???????? | // 83c40c | add esp, 0xc // 85c0 | test eax, eax // 755d | jne 0x5f // 8b435c | mov eax, dword ptr [ebx + 0x5c] $sequence_6 = { ff5518 83c40c 85c0 756f 8d4dbc 57 51 } // n = 7, score = 100 // ff5518 | call dword ptr [ebp + 0x18] // 83c40c | add esp, 0xc // 85c0 | test eax, eax // 756f | jne 0x71 // 8d4dbc | lea ecx, [ebp - 0x44] // 57 | push edi // 51 | push ecx $sequence_7 = { c745fc00000000 8b7e58 50 83c707 c1ef03 e8???????? 8d4de4 } // n = 7, score = 100 // c745fc00000000 | mov dword ptr [ebp - 4], 0 // 8b7e58 | mov edi, dword ptr [esi + 0x58] // 50 | push eax // 83c707 | add edi, 7 // c1ef03 | shr edi, 3 // e8???????? | // 8d4de4 | lea ecx, [ebp - 0x1c] $sequence_8 = { f3a5 8bca 8b550c 83e103 03d0 f3a4 8b4d10 } // n = 7, score = 100 // f3a5 | rep movsd dword ptr es:[edi], dword ptr [esi] // 8bca | mov ecx, edx // 8b550c | mov edx, dword ptr [ebp + 0xc] // 83e103 | and ecx, 3 // 03d0 | add edx, eax // f3a4 | rep movsb byte ptr es:[edi], byte ptr [esi] // 8b4d10 | mov ecx, dword ptr [ebp + 0x10] $sequence_9 = { 8916 894604 83c40c 83c608 4f 75de 8d734c } // n = 7, score = 100 // 8916 | mov dword ptr [esi], edx // 894604 | mov dword ptr [esi + 4], eax // 83c40c | add esp, 0xc // 83c608 | add esi, 8 // 4f | dec edi // 75de | jne 0xffffffe0 // 8d734c | lea esi, [ebx + 0x4c] condition: 7 of them and filesize < 893708 }
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