Information Stealer that searches for sensitive documents and uploads its results to an FTP server. Skips files with known Ryuk extensions.
rule win_ryuk_stealer_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-04-08" version = "1" description = "Detects win.ryuk_stealer." 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.ryuk_stealer" malpedia_rule_date = "20220405" malpedia_hash = "ecd38294bd47d5589be5cd5490dc8bb4804afc2a" malpedia_version = "20220411" 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 = { f7f1 8bf2 e8???????? 8bc8 33d2 8bc6 f7f1 } // n = 7, score = 800 // f7f1 | div ecx // 8bf2 | mov esi, edx // e8???????? | // 8bc8 | mov ecx, eax // 33d2 | xor edx, edx // 8bc6 | mov eax, esi // f7f1 | div ecx $sequence_1 = { 99 b9a0860100 f7f9 81c2f8240100 52 } // n = 5, score = 800 // 99 | cdq // b9a0860100 | mov ecx, 0x186a0 // f7f9 | idiv ecx // 81c2f8240100 | add edx, 0x124f8 // 52 | push edx $sequence_2 = { ff15???????? 83f805 740a b9???????? e8???????? } // n = 5, score = 800 // ff15???????? | // 83f805 | cmp eax, 5 // 740a | je 0xc // b9???????? | // e8???????? | $sequence_3 = { e8???????? 99 b9a0860100 f7f9 81c2a8610000 } // n = 5, score = 800 // e8???????? | // 99 | cdq // b9a0860100 | mov ecx, 0x186a0 // f7f9 | idiv ecx // 81c2a8610000 | add edx, 0x61a8 $sequence_4 = { 83ff01 755d 8bcb e8???????? } // n = 4, score = 800 // 83ff01 | cmp edi, 1 // 755d | jne 0x5f // 8bcb | mov ecx, ebx // e8???????? | $sequence_5 = { 99 b9a0860100 f7f9 81c2a8610000 52 } // n = 5, score = 800 // 99 | cdq // b9a0860100 | mov ecx, 0x186a0 // f7f9 | idiv ecx // 81c2a8610000 | add edx, 0x61a8 // 52 | push edx $sequence_6 = { 8bf2 e8???????? 8bc8 33d2 8bc6 f7f1 6a0a } // n = 7, score = 800 // 8bf2 | mov esi, edx // e8???????? | // 8bc8 | mov ecx, eax // 33d2 | xor edx, edx // 8bc6 | mov eax, esi // f7f1 | div ecx // 6a0a | push 0xa $sequence_7 = { 0fb701 8d4902 6685c0 75f5 6a04 6800100000 6815270000 } // n = 7, score = 800 // 0fb701 | movzx eax, word ptr [ecx] // 8d4902 | lea ecx, dword ptr [ecx + 2] // 6685c0 | test ax, ax // 75f5 | jne 0xfffffff7 // 6a04 | push 4 // 6800100000 | push 0x1000 // 6815270000 | push 0x2715 $sequence_8 = { 83c40c ff15???????? 33d2 b910270000 f7f1 } // n = 5, score = 800 // 83c40c | add esp, 0xc // ff15???????? | // 33d2 | xor edx, edx // b910270000 | mov ecx, 0x2710 // f7f1 | div ecx $sequence_9 = { e8???????? 99 b9a0860100 f7f9 81c2a8610000 52 ff15???????? } // n = 7, score = 800 // e8???????? | // 99 | cdq // b9a0860100 | mov ecx, 0x186a0 // f7f9 | idiv ecx // 81c2a8610000 | add edx, 0x61a8 // 52 | push edx // ff15???????? | condition: 7 of them and filesize < 368640 }
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