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rule win_webc2_greencat_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.webc2_greencat." 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.webc2_greencat" malpedia_rule_date = "20260105" malpedia_hash = "19b79e7cab4eaf532122e5b45a77dd8f6bb5cc79" malpedia_version = "20251219" 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 = { 59 0f85ab000000 bf28010000 8d85c0fdffff 57 53 } // n = 6, score = 100 // 59 | pop ecx // 0f85ab000000 | jne 0xb1 // bf28010000 | mov edi, 0x128 // 8d85c0fdffff | lea eax, [ebp - 0x240] // 57 | push edi // 53 | push ebx $sequence_1 = { 50 e8???????? 53 50 894614 } // n = 5, score = 100 // 50 | push eax // e8???????? | // 53 | push ebx // 50 | push eax // 894614 | mov dword ptr [esi + 0x14], eax $sequence_2 = { 8d4dac ff750c e8???????? 85c0 7511 6830750000 } // n = 6, score = 100 // 8d4dac | lea ecx, [ebp - 0x54] // ff750c | push dword ptr [ebp + 0xc] // e8???????? | // 85c0 | test eax, eax // 7511 | jne 0x13 // 6830750000 | push 0x7530 $sequence_3 = { 53 ff15???????? 55 e8???????? 3bf3 59 7407 } // n = 7, score = 100 // 53 | push ebx // ff15???????? | // 55 | push ebp // e8???????? | // 3bf3 | cmp esi, ebx // 59 | pop ecx // 7407 | je 9 $sequence_4 = { e9???????? 8d45ac 50 ff750c e8???????? e9???????? 8b4508 } // n = 7, score = 100 // e9???????? | // 8d45ac | lea eax, [ebp - 0x54] // 50 | push eax // ff750c | push dword ptr [ebp + 0xc] // e8???????? | // e9???????? | // 8b4508 | mov eax, dword ptr [ebp + 8] $sequence_5 = { 58 e9???????? 56 be00010000 57 56 e8???????? } // n = 7, score = 100 // 58 | pop eax // e9???????? | // 56 | push esi // be00010000 | mov esi, 0x100 // 57 | push edi // 56 | push esi // e8???????? | $sequence_6 = { 5a 8b7508 668950f8 8950fc 668910 66895802 66895804 } // n = 7, score = 100 // 5a | pop edx // 8b7508 | mov esi, dword ptr [ebp + 8] // 668950f8 | mov word ptr [eax - 8], dx // 8950fc | mov dword ptr [eax - 4], edx // 668910 | mov word ptr [eax], dx // 66895802 | mov word ptr [eax + 2], bx // 66895804 | mov word ptr [eax + 4], bx $sequence_7 = { 8d0c30 03c6 2945ec 03d9 85f6 75ac 3975fc } // n = 7, score = 100 // 8d0c30 | lea ecx, [eax + esi] // 03c6 | add eax, esi // 2945ec | sub dword ptr [ebp - 0x14], eax // 03d9 | add ebx, ecx // 85f6 | test esi, esi // 75ac | jne 0xffffffae // 3975fc | cmp dword ptr [ebp - 4], esi $sequence_8 = { ff15???????? 83f8ff 8945ec 7411 ff15???????? 3db7000000 0f84de010000 } // n = 7, score = 100 // ff15???????? | // 83f8ff | cmp eax, -1 // 8945ec | mov dword ptr [ebp - 0x14], eax // 7411 | je 0x13 // ff15???????? | // 3db7000000 | cmp eax, 0xb7 // 0f84de010000 | je 0x1e4 $sequence_9 = { 50 ff15???????? 3bc7 59 7405 a3???????? 8a45ff } // n = 7, score = 100 // 50 | push eax // ff15???????? | // 3bc7 | cmp eax, edi // 59 | pop ecx // 7405 | je 7 // a3???????? | // 8a45ff | mov al, byte ptr [ebp - 1] condition: 7 of them and filesize < 57344 }
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