PyLocky is a ransomware that tries to pass off as Locky in its ransom note. It is written in Python and packaged with PyInstaller.
rule win_pylocky_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/win.pylocky" 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 = { 8bc2 c1e818 331c8588224200 0fb6c2 } // n = 4, score = 100 // 8bc2 | mov eax, edx // c1e818 | shr eax, 0x18 // 331c8588224200 | xor ebx, dword ptr [eax*4 + 0x422288] // 0fb6c2 | movzx eax, dl $sequence_1 = { 0f84e8000000 8d442410 50 ff15???????? 83c404 } // n = 5, score = 100 // 0f84e8000000 | je 0xee // 8d442410 | lea eax, [esp + 0x10] // 50 | push eax // ff15???????? | // 83c404 | add esp, 4 $sequence_2 = { 8944241c 6800100000 56 e8???????? 83c410 } // n = 5, score = 100 // 8944241c | mov dword ptr [esp + 0x1c], eax // 6800100000 | push 0x1000 // 56 | push esi // e8???????? | // 83c410 | add esp, 0x10 $sequence_3 = { 57 8db8e8a34300 57 ff15???????? ff0d???????? 83ef18 83ee01 } // n = 7, score = 100 // 57 | push edi // 8db8e8a34300 | lea edi, [eax + 0x43a3e8] // 57 | push edi // ff15???????? | // ff0d???????? | // 83ef18 | sub edi, 0x18 // 83ee01 | sub esi, 1 $sequence_4 = { e8???????? 83c408 85c0 75b6 56 57 e8???????? } // n = 7, score = 100 // e8???????? | // 83c408 | add esp, 8 // 85c0 | test eax, eax // 75b6 | jne 0xffffffb8 // 56 | push esi // 57 | push edi // e8???????? | $sequence_5 = { 83e63f c1f806 6bce30 8945f4 8b048510a14300 894df0 } // n = 6, score = 100 // 83e63f | and esi, 0x3f // c1f806 | sar eax, 6 // 6bce30 | imul ecx, esi, 0x30 // 8945f4 | mov dword ptr [ebp - 0xc], eax // 8b048510a14300 | mov eax, dword ptr [eax*4 + 0x43a110] // 894df0 | mov dword ptr [ebp - 0x10], ecx $sequence_6 = { 894634 85c0 7505 8bc7 } // n = 4, score = 100 // 894634 | mov dword ptr [esi + 0x34], eax // 85c0 | test eax, eax // 7505 | jne 7 // 8bc7 | mov eax, edi $sequence_7 = { ff75f4 56 e8???????? 83c40c 57 e8???????? 59 } // n = 7, score = 100 // ff75f4 | push dword ptr [ebp - 0xc] // 56 | push esi // e8???????? | // 83c40c | add esp, 0xc // 57 | push edi // e8???????? | // 59 | pop ecx condition: 7 of them and filesize < 626688 }
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