Ransomware.
rule win_xiaoba_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.xiaoba." 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.xiaoba" malpedia_rule_date = "20231130" malpedia_hash = "fc8a0e9f343f6d6ded9e7df1a64dac0cc68d7351" malpedia_version = "20230808" 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 = { 58 8945ec e9???????? 8b5dfc 83c320 895dd0 6801030080 } // n = 7, score = 100 // 58 | pop eax // 8945ec | mov dword ptr [ebp - 0x14], eax // e9???????? | // 8b5dfc | mov ebx, dword ptr [ebp - 4] // 83c320 | add ebx, 0x20 // 895dd0 | mov dword ptr [ebp - 0x30], ebx // 6801030080 | push 0x80000301 $sequence_1 = { b801000000 c20c00 8b9024010000 8b44240c 8910 b801000000 c20c00 } // n = 7, score = 100 // b801000000 | mov eax, 1 // c20c00 | ret 0xc // 8b9024010000 | mov edx, dword ptr [eax + 0x124] // 8b44240c | mov eax, dword ptr [esp + 0xc] // 8910 | mov dword ptr [eax], edx // b801000000 | mov eax, 1 // c20c00 | ret 0xc $sequence_2 = { 8b5c243c 8b7c2464 8b542428 8b442430 03c3 42 89442430 } // n = 7, score = 100 // 8b5c243c | mov ebx, dword ptr [esp + 0x3c] // 8b7c2464 | mov edi, dword ptr [esp + 0x64] // 8b542428 | mov edx, dword ptr [esp + 0x28] // 8b442430 | mov eax, dword ptr [esp + 0x30] // 03c3 | add eax, ebx // 42 | inc edx // 89442430 | mov dword ptr [esp + 0x30], eax $sequence_3 = { dc442410 dd5c2410 e9???????? db8740010000 dc6c2418 dd5c2418 e9???????? } // n = 7, score = 100 // dc442410 | fadd qword ptr [esp + 0x10] // dd5c2410 | fstp qword ptr [esp + 0x10] // e9???????? | // db8740010000 | fild dword ptr [edi + 0x140] // dc6c2418 | fsubr qword ptr [esp + 0x18] // dd5c2418 | fstp qword ptr [esp + 0x18] // e9???????? | $sequence_4 = { 8b8894010000 33d2 85c9 0f95c2 8bc2 c20800 8b90b4010000 } // n = 7, score = 100 // 8b8894010000 | mov ecx, dword ptr [eax + 0x194] // 33d2 | xor edx, edx // 85c9 | test ecx, ecx // 0f95c2 | setne dl // 8bc2 | mov eax, edx // c20800 | ret 8 // 8b90b4010000 | mov edx, dword ptr [eax + 0x1b4] $sequence_5 = { 8d54b500 8b3c02 8d44f500 83c704 57 50 e8???????? } // n = 7, score = 100 // 8d54b500 | lea edx, [ebp + esi*4] // 8b3c02 | mov edi, dword ptr [edx + eax] // 8d44f500 | lea eax, [ebp + esi*8] // 83c704 | add edi, 4 // 57 | push edi // 50 | push eax // e8???????? | $sequence_6 = { 85c9 7519 8b54240c 33c9 890a 8b8820010000 894a04 } // n = 7, score = 100 // 85c9 | test ecx, ecx // 7519 | jne 0x1b // 8b54240c | mov edx, dword ptr [esp + 0xc] // 33c9 | xor ecx, ecx // 890a | mov dword ptr [edx], ecx // 8b8820010000 | mov ecx, dword ptr [eax + 0x120] // 894a04 | mov dword ptr [edx + 4], ecx $sequence_7 = { 85c0 be???????? 7505 be???????? e8???????? 8b4008 56 } // n = 7, score = 100 // 85c0 | test eax, eax // be???????? | // 7505 | jne 7 // be???????? | // e8???????? | // 8b4008 | mov eax, dword ptr [eax + 8] // 56 | push esi $sequence_8 = { 8b10 52 e8???????? 83c404 8b4c2474 8901 8d4c2414 } // n = 7, score = 100 // 8b10 | mov edx, dword ptr [eax] // 52 | push edx // e8???????? | // 83c404 | add esp, 4 // 8b4c2474 | mov ecx, dword ptr [esp + 0x74] // 8901 | mov dword ptr [ecx], eax // 8d4c2414 | lea ecx, [esp + 0x14] $sequence_9 = { 8903 8965e8 6800000000 6800000000 6800000000 ff75f0 6800000000 } // n = 7, score = 100 // 8903 | mov dword ptr [ebx], eax // 8965e8 | mov dword ptr [ebp - 0x18], esp // 6800000000 | push 0 // 6800000000 | push 0 // 6800000000 | push 0 // ff75f0 | push dword ptr [ebp - 0x10] // 6800000000 | push 0 condition: 7 of them and filesize < 5177344 }
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