Ransomware.
rule win_knot_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.knot." 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.knot" 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 = { 50 8b8ddcfdffff 51 6a00 6a00 6a01 } // n = 6, score = 200 // 50 | push eax // 8b8ddcfdffff | mov ecx, dword ptr [ebp - 0x224] // 51 | push ecx // 6a00 | push 0 // 6a00 | push 0 // 6a01 | push 1 $sequence_1 = { 55 8bec 81ec34010000 6a00 } // n = 4, score = 200 // 55 | push ebp // 8bec | mov ebp, esp // 81ec34010000 | sub esp, 0x134 // 6a00 | push 0 $sequence_2 = { 6a18 6a00 6a00 68???????? ff15???????? 8d95f0f9ffff } // n = 6, score = 200 // 6a18 | push 0x18 // 6a00 | push 0 // 6a00 | push 0 // 68???????? | // ff15???????? | // 8d95f0f9ffff | lea edx, [ebp - 0x610] $sequence_3 = { ff15???????? 83c408 6a01 6a00 } // n = 4, score = 200 // ff15???????? | // 83c408 | add esp, 8 // 6a01 | push 1 // 6a00 | push 0 $sequence_4 = { 83bdd4fdffff00 7443 8b85d8fdffff 50 8b8ddcfdffff 51 } // n = 6, score = 200 // 83bdd4fdffff00 | cmp dword ptr [ebp - 0x22c], 0 // 7443 | je 0x45 // 8b85d8fdffff | mov eax, dword ptr [ebp - 0x228] // 50 | push eax // 8b8ddcfdffff | mov ecx, dword ptr [ebp - 0x224] // 51 | push ecx $sequence_5 = { 6800000040 8d95e0fdffff 52 ff15???????? } // n = 4, score = 200 // 6800000040 | push 0x40000000 // 8d95e0fdffff | lea edx, [ebp - 0x220] // 52 | push edx // ff15???????? | $sequence_6 = { ff15???????? 8b55ec 52 ff15???????? 8b45e8 50 ff15???????? } // n = 7, score = 200 // ff15???????? | // 8b55ec | mov edx, dword ptr [ebp - 0x14] // 52 | push edx // ff15???????? | // 8b45e8 | mov eax, dword ptr [ebp - 0x18] // 50 | push eax // ff15???????? | $sequence_7 = { 6a00 6a00 68???????? ff15???????? 8d95f0f9ffff 52 e8???????? } // n = 7, score = 200 // 6a00 | push 0 // 6a00 | push 0 // 68???????? | // ff15???????? | // 8d95f0f9ffff | lea edx, [ebp - 0x610] // 52 | push edx // e8???????? | $sequence_8 = { 52 ff15???????? 85c0 7507 32c0 e9???????? c785d8fdffff00000000 } // n = 7, score = 200 // 52 | push edx // ff15???????? | // 85c0 | test eax, eax // 7507 | jne 9 // 32c0 | xor al, al // e9???????? | // c785d8fdffff00000000 | mov dword ptr [ebp - 0x228], 0 $sequence_9 = { 83c408 68???????? 8b8d74f7ffff 51 e8???????? } // n = 5, score = 200 // 83c408 | add esp, 8 // 68???????? | // 8b8d74f7ffff | mov ecx, dword ptr [ebp - 0x88c] // 51 | push ecx // e8???????? | condition: 7 of them and filesize < 59392 }
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