Actor(s): Sofacy
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rule win_koadic_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2020-12-22" version = "1" description = "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.koadic" malpedia_rule_date = "20201222" malpedia_hash = "30354d830a29f0fbd3714d93d94dea941d77a130" malpedia_version = "20201023" 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 = { 56 ff75fc 56 6838330000 e9???????? 8bc3 2d03020000 } // n = 7, score = 100 // 56 | push esi // ff75fc | push dword ptr [ebp - 4] // 56 | push esi // 6838330000 | push 0x3338 // e9???????? | // 8bc3 | mov eax, ebx // 2d03020000 | sub eax, 0x203 $sequence_1 = { 5b c20400 55 8bec 837d0800 7414 } // n = 6, score = 100 // 5b | pop ebx // c20400 | ret 4 // 55 | push ebp // 8bec | mov ebp, esp // 837d0800 | cmp dword ptr [ebp + 8], 0 // 7414 | je 0x16 $sequence_2 = { 7439 f7c300000001 740c f7df 1bff } // n = 5, score = 100 // 7439 | je 0x3b // f7c300000001 | test ebx, 0x1000000 // 740c | je 0xe // f7df | neg edi // 1bff | sbb edi, edi $sequence_3 = { 83c424 5b c20800 31c0 50 } // n = 5, score = 100 // 83c424 | add esp, 0x24 // 5b | pop ebx // c20800 | ret 8 // 31c0 | xor eax, eax // 50 | push eax $sequence_4 = { 53 ff75fc ff75fc 683c330000 e9???????? 6685ff 7427 } // n = 7, score = 100 // 53 | push ebx // ff75fc | push dword ptr [ebp - 4] // ff75fc | push dword ptr [ebp - 4] // 683c330000 | push 0x333c // e9???????? | // 6685ff | test di, di // 7427 | je 0x29 $sequence_5 = { 03f7 83fbff 7473 4b 85db 7f6e 8b7c241c } // n = 7, score = 100 // 03f7 | add esi, edi // 83fbff | cmp ebx, -1 // 7473 | je 0x75 // 4b | dec ebx // 85db | test ebx, ebx // 7f6e | jg 0x70 // 8b7c241c | mov edi, dword ptr [esp + 0x1c] $sequence_6 = { 53 6a00 ff35???????? 894514 ff15???????? 8bf8 } // n = 6, score = 100 // 53 | push ebx // 6a00 | push 0 // ff35???????? | // 894514 | mov dword ptr [ebp + 0x14], eax // ff15???????? | // 8bf8 | mov edi, eax $sequence_7 = { 4e 85ff 75bc 85f6 7416 4e 8910 } // n = 7, score = 100 // 4e | dec esi // 85ff | test edi, edi // 75bc | jne 0xffffffbe // 85f6 | test esi, esi // 7416 | je 0x18 // 4e | dec esi // 8910 | mov dword ptr [eax], edx $sequence_8 = { c705????????c49d4000 c705????????01000000 837d1c00 7507 c7451c02104100 8b4d20 6a00 } // n = 7, score = 100 // c705????????c49d4000 | // c705????????01000000 | // 837d1c00 | cmp dword ptr [ebp + 0x1c], 0 // 7507 | jne 9 // c7451c02104100 | mov dword ptr [ebp + 0x1c], 0x411002 // 8b4d20 | mov ecx, dword ptr [ebp + 0x20] // 6a00 | push 0 $sequence_9 = { 83c102 894d08 eb09 8b5508 83c201 895508 e9???????? } // n = 7, score = 100 // 83c102 | add ecx, 2 // 894d08 | mov dword ptr [ebp + 8], ecx // eb09 | jmp 0xb // 8b5508 | mov edx, dword ptr [ebp + 8] // 83c201 | add edx, 1 // 895508 | mov dword ptr [ebp + 8], edx // e9???????? | condition: 7 of them and filesize < 180224 }
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