Ransomware.
rule win_mrdec_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.mrdec." 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.mrdec" 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 = { c64446fa00 57 56 e8???????? 68???????? 56 e8???????? } // n = 7, score = 100 // c64446fa00 | mov byte ptr [esi + eax*2 - 6], 0 // 57 | push edi // 56 | push esi // e8???????? | // 68???????? | // 56 | push esi // e8???????? | $sequence_1 = { 6a00 8d45cc 50 68ef000000 68???????? } // n = 5, score = 100 // 6a00 | push 0 // 8d45cc | lea eax, [ebp - 0x34] // 50 | push eax // 68ef000000 | push 0xef // 68???????? | $sequence_2 = { 50 ff75f0 6a00 6a00 6a00 ff75e8 e8???????? } // n = 7, score = 100 // 50 | push eax // ff75f0 | push dword ptr [ebp - 0x10] // 6a00 | push 0 // 6a00 | push 0 // 6a00 | push 0 // ff75e8 | push dword ptr [ebp - 0x18] // e8???????? | $sequence_3 = { 7532 68dc050000 ff75dc 68???????? e8???????? } // n = 5, score = 100 // 7532 | jne 0x34 // 68dc050000 | push 0x5dc // ff75dc | push dword ptr [ebp - 0x24] // 68???????? | // e8???????? | $sequence_4 = { 6a00 6814010000 68???????? ff75d8 e8???????? 8d3550514000 } // n = 6, score = 100 // 6a00 | push 0 // 6814010000 | push 0x114 // 68???????? | // ff75d8 | push dword ptr [ebp - 0x28] // e8???????? | // 8d3550514000 | lea esi, [0x405150] $sequence_5 = { 8bec ff7508 6a40 e8???????? 0bc0 750c 68c8000000 } // n = 7, score = 100 // 8bec | mov ebp, esp // ff7508 | push dword ptr [ebp + 8] // 6a40 | push 0x40 // e8???????? | // 0bc0 | or eax, eax // 750c | jne 0xe // 68c8000000 | push 0xc8 $sequence_6 = { 81c700020000 68???????? 57 e8???????? 68???????? 57 e8???????? } // n = 7, score = 100 // 81c700020000 | add edi, 0x200 // 68???????? | // 57 | push edi // e8???????? | // 68???????? | // 57 | push edi // e8???????? | $sequence_7 = { 59 51 80c141 884808 ff05???????? 6a00 6a00 } // n = 7, score = 100 // 59 | pop ecx // 51 | push ecx // 80c141 | add cl, 0x41 // 884808 | mov byte ptr [eax + 8], cl // ff05???????? | // 6a00 | push 0 // 6a00 | push 0 $sequence_8 = { 6a02 e8???????? 0bc0 0f8530010000 c745f000400000 ff75f0 } // n = 6, score = 100 // 6a02 | push 2 // e8???????? | // 0bc0 | or eax, eax // 0f8530010000 | jne 0x136 // c745f000400000 | mov dword ptr [ebp - 0x10], 0x4000 // ff75f0 | push dword ptr [ebp - 0x10] $sequence_9 = { 6a00 6a00 e8???????? ff75dc e8???????? } // n = 5, score = 100 // 6a00 | push 0 // 6a00 | push 0 // e8???????? | // ff75dc | push dword ptr [ebp - 0x24] // e8???????? | condition: 7 of them and filesize < 44864 }
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