The Chinese threat actor has used a custom backdoor dubbed "Scieron" over years in several campaigns according to SentinelLABS.
rule win_scieron_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.scieron." 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.scieron" 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 = { 895c2420 33ff ff15???????? 85c0 7554 ff15???????? 53 } // n = 7, score = 100 // 895c2420 | mov dword ptr [esp + 0x20], ebx // 33ff | xor edi, edi // ff15???????? | // 85c0 | test eax, eax // 7554 | jne 0x56 // ff15???????? | // 53 | push ebx $sequence_1 = { 40 c20c00 81ec0c020000 53 8b1d???????? } // n = 5, score = 100 // 40 | inc eax // c20c00 | ret 0xc // 81ec0c020000 | sub esp, 0x20c // 53 | push ebx // 8b1d???????? | $sequence_2 = { 897d0c 6a03 e8???????? 8bf8 83c410 } // n = 5, score = 100 // 897d0c | mov dword ptr [ebp + 0xc], edi // 6a03 | push 3 // e8???????? | // 8bf8 | mov edi, eax // 83c410 | add esp, 0x10 $sequence_3 = { ebaf 8b45fc 56 e8???????? ebb9 ff75fc } // n = 6, score = 100 // ebaf | jmp 0xffffffb1 // 8b45fc | mov eax, dword ptr [ebp - 4] // 56 | push esi // e8???????? | // ebb9 | jmp 0xffffffbb // ff75fc | push dword ptr [ebp - 4] $sequence_4 = { 85f6 0f95c0 5f 5e 5b c9 c3 } // n = 7, score = 100 // 85f6 | test esi, esi // 0f95c0 | setne al // 5f | pop edi // 5e | pop esi // 5b | pop ebx // c9 | leave // c3 | ret $sequence_5 = { 83c40c 85c0 7454 8b1d???????? } // n = 4, score = 100 // 83c40c | add esp, 0xc // 85c0 | test eax, eax // 7454 | je 0x56 // 8b1d???????? | $sequence_6 = { 8b861c020000 85c0 7463 b980000000 } // n = 4, score = 100 // 8b861c020000 | mov eax, dword ptr [esi + 0x21c] // 85c0 | test eax, eax // 7463 | je 0x65 // b980000000 | mov ecx, 0x80 $sequence_7 = { 75de 6a00 ff15???????? 50 ff742418 33ff } // n = 6, score = 100 // 75de | jne 0xffffffe0 // 6a00 | push 0 // ff15???????? | // 50 | push eax // ff742418 | push dword ptr [esp + 0x18] // 33ff | xor edi, edi $sequence_8 = { 3bfe 7419 8d4574 50 57 56 } // n = 6, score = 100 // 3bfe | cmp edi, esi // 7419 | je 0x1b // 8d4574 | lea eax, [ebp + 0x74] // 50 | push eax // 57 | push edi // 56 | push esi $sequence_9 = { 53 8b1d???????? 55 33c0 57 } // n = 5, score = 100 // 53 | push ebx // 8b1d???????? | // 55 | push ebp // 33c0 | xor eax, eax // 57 | push edi condition: 7 of them and filesize < 100352 }
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