Actor(s): APT28
Suspected Zebrocy loader written in Nim.
rule win_unidentified_078_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.unidentified_078." 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.unidentified_078" 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 = { 7d21 8a440b10 3c5c 7419 } // n = 4, score = 200 // 7d21 | dec ecx // 8a440b10 | mov ecx, dword ptr [ecx] // 3c5c | dec eax // 7419 | cmp ecx, 7 $sequence_1 = { e8???????? 84c0 7467 f60701 } // n = 4, score = 200 // e8???????? | // 84c0 | dec eax // 7467 | dec eax // f60701 | lea edx, [0x21e0a] $sequence_2 = { e9???????? 80fa5b 7f3c 80fa28 0f8d94010000 } // n = 5, score = 200 // e9???????? | // 80fa5b | lea edx, [ebx + 0x30a8] // 7f3c | dec esp // 80fa28 | mov ecx, ebx // 0f8d94010000 | dec ebp $sequence_3 = { 80fa0d 0f8421010000 80fa1b 0f8576010000 ba02000000 e8???????? } // n = 6, score = 200 // 80fa0d | dec edx // 0f8421010000 | test dword ptr [eax + eax*8 + 0x10], edx // 80fa1b | setne dl // 0f8576010000 | mov eax, edx // ba02000000 | dec ecx // e8???????? | $sequence_4 = { 80fa7e 0f8f02010000 e9???????? ba02000000 } // n = 4, score = 200 // 80fa7e | mov ecx, dword ptr [edx + edx*8] // 0f8f02010000 | dec ebp // e9???????? | // ba02000000 | mov dword ptr [ebx], ecx $sequence_5 = { b901010000 ff15???????? 85c0 740e e8???????? } // n = 5, score = 200 // b901010000 | mov ecx, ecx // ff15???????? | // 85c0 | dec eax // 740e | and ecx, 0xfffff000 // e8???????? | $sequence_6 = { 0f8cee000000 80fa0d 0f8421010000 80fa1b 0f8576010000 } // n = 5, score = 200 // 0f8cee000000 | movsx edx, byte ptr [esp + esi + 0x10] // 80fa0d | dec eax // 0f8421010000 | mov ecx, dword ptr [ebx] // 80fa1b | inc ecx // 0f8576010000 | mov ecx, edi $sequence_7 = { 0f8f18010000 80fa23 0f8d82010000 ba02000000 } // n = 4, score = 200 // 0f8f18010000 | jmp 0x1b // 80fa23 | mov ecx, 0x3b0001 // 0f8d82010000 | dec eax // ba02000000 | ja 0x138 $sequence_8 = { 753f a900004011 7521 a900000600 } // n = 4, score = 200 // 753f | dec ebp // a900004011 | test ebx, ebx // 7521 | je 0x9b // a900000600 | dec ecx $sequence_9 = { 0f8d94010000 80fa26 0f8f18010000 80fa23 0f8d82010000 } // n = 5, score = 200 // 0f8d94010000 | sub esi, edi // 80fa26 | xor edx, edx // 0f8f18010000 | dec eax // 80fa23 | mov ecx, ebp // 0f8d82010000 | inc esp condition: 7 of them and filesize < 688128 }
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