General purpose backdoor
rule osx_systemd_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2020-10-14" version = "1" description = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.5.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/osx.systemd" malpedia_rule_date = "20201014" malpedia_hash = "a7e3bd57eaf12bf3ea29a863c041091ba3af9ac9" malpedia_version = "20201014" 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 = { 49 8b0424 49 8b4c2408 49 894d28 } // n = 6, score = 100 // 49 | dec ecx // 8b0424 | mov eax, dword ptr [esp] // 49 | dec ecx // 8b4c2408 | mov ecx, dword ptr [esp + 8] // 49 | dec ecx // 894d28 | mov dword ptr [ebp + 0x28], ecx $sequence_1 = { 41 01f2 41 ffc5 41 89f8 } // n = 6, score = 100 // 41 | inc ecx // 01f2 | add edx, esi // 41 | inc ecx // ffc5 | inc ebp // 41 | inc ecx // 89f8 | mov eax, edi $sequence_2 = { f00fc148f8 85c9 7fa6 48 8d75b8 e8???????? } // n = 6, score = 100 // f00fc148f8 | lock xadd dword ptr [eax - 8], ecx // 85c9 | test ecx, ecx // 7fa6 | jg 0xffffffa8 // 48 | dec eax // 8d75b8 | lea esi, [ebp - 0x48] // e8???????? | $sequence_3 = { 49 3314c1 48 89f8 48 c1e80d 48 } // n = 7, score = 100 // 49 | dec ecx // 3314c1 | xor edx, dword ptr [ecx + eax*8] // 48 | dec eax // 89f8 | mov eax, edi // 48 | dec eax // c1e80d | shr eax, 0xd // 48 | dec eax $sequence_4 = { 48 898578ffffff 48 8d7d88 48 8d7580 48 } // n = 7, score = 100 // 48 | dec eax // 898578ffffff | mov dword ptr [ebp - 0x88], eax // 48 | dec eax // 8d7d88 | lea edi, [ebp - 0x78] // 48 | dec eax // 8d7580 | lea esi, [ebp - 0x80] // 48 | dec eax $sequence_5 = { c1e01c 48 09c8 48 338678010000 48 89c1 } // n = 7, score = 100 // c1e01c | shl eax, 0x1c // 48 | dec eax // 09c8 | or eax, ecx // 48 | dec eax // 338678010000 | xor eax, dword ptr [esi + 0x178] // 48 | dec eax // 89c1 | mov ecx, eax $sequence_6 = { 89f2 e8???????? 31c9 b8???????? 0f1f840000000000 4c } // n = 6, score = 100 // 89f2 | mov edx, esi // e8???????? | // 31c9 | xor ecx, ecx // b8???????? | // 0f1f840000000000 | nop dword ptr [eax + eax] // 4c | dec esp $sequence_7 = { 89f5 49 89fe 49 8b4e08 49 3b4e10 } // n = 7, score = 100 // 89f5 | mov ebp, esi // 49 | dec ecx // 89fe | mov esi, edi // 49 | dec ecx // 8b4e08 | mov ecx, dword ptr [esi + 8] // 49 | dec ecx // 3b4e10 | cmp ecx, dword ptr [esi + 0x10] $sequence_8 = { e8???????? c7833c04000000000000 4c 89f7 48 83c408 5b } // n = 7, score = 100 // e8???????? | // c7833c04000000000000 | mov dword ptr [ebx + 0x43c], 0 // 4c | dec esp // 89f7 | mov edi, esi // 48 | dec eax // 83c408 | add esp, 8 // 5b | pop ebx $sequence_9 = { 48 31f8 48 01d0 be81e6a1d8 48 01c6 } // n = 7, score = 100 // 48 | dec eax // 31f8 | xor eax, edi // 48 | dec eax // 01d0 | add eax, edx // be81e6a1d8 | mov esi, 0xd8a1e681 // 48 | dec eax // 01c6 | add esi, eax condition: 7 of them and filesize < 381108 }
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