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rule win_fatal_rat_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" version = "1" description = "Detects win.fatal_rat." 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.fatal_rat" malpedia_rule_date = "20220513" malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26" malpedia_version = "20220516" 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 = { 8b06 5f 5e c3 55 8bec } // n = 6, score = 100 // 8b06 | mov eax, dword ptr [esi] // 5f | pop edi // 5e | pop esi // c3 | ret // 55 | push ebp // 8bec | mov ebp, esp $sequence_1 = { c6857dfeffff78 c6857efeffff65 889d7ffeffff c68534ffffff61 c68535ffffff76 c68536ffffff67 } // n = 6, score = 100 // c6857dfeffff78 | mov byte ptr [ebp - 0x183], 0x78 // c6857efeffff65 | mov byte ptr [ebp - 0x182], 0x65 // 889d7ffeffff | mov byte ptr [ebp - 0x181], bl // c68534ffffff61 | mov byte ptr [ebp - 0xcc], 0x61 // c68535ffffff76 | mov byte ptr [ebp - 0xcb], 0x76 // c68536ffffff67 | mov byte ptr [ebp - 0xca], 0x67 $sequence_2 = { 894608 ffd7 68???????? 894628 ff7608 ffd7 68???????? } // n = 7, score = 100 // 894608 | mov dword ptr [esi + 8], eax // ffd7 | call edi // 68???????? | // 894628 | mov dword ptr [esi + 0x28], eax // ff7608 | push dword ptr [esi + 8] // ffd7 | call edi // 68???????? | $sequence_3 = { 3bd0 7502 8bf8 48 ebdf 2bf9 57 } // n = 7, score = 100 // 3bd0 | cmp edx, eax // 7502 | jne 4 // 8bf8 | mov edi, eax // 48 | dec eax // ebdf | jmp 0xffffffe1 // 2bf9 | sub edi, ecx // 57 | push edi $sequence_4 = { 33ff 57 57 57 57 68???????? eb81 } // n = 7, score = 100 // 33ff | xor edi, edi // 57 | push edi // 57 | push edi // 57 | push edi // 57 | push edi // 68???????? | // eb81 | jmp 0xffffff83 $sequence_5 = { 75f7 5e 8bc7 5f 5d c3 55 } // n = 7, score = 100 // 75f7 | jne 0xfffffff9 // 5e | pop esi // 8bc7 | mov eax, edi // 5f | pop edi // 5d | pop ebp // c3 | ret // 55 | push ebp $sequence_6 = { 6685c0 741f 83ffff 7e1a 83fe40 7e15 83fe5d } // n = 7, score = 100 // 6685c0 | test ax, ax // 741f | je 0x21 // 83ffff | cmp edi, -1 // 7e1a | jle 0x1c // 83fe40 | cmp esi, 0x40 // 7e15 | jle 0x17 // 83fe5d | cmp esi, 0x5d $sequence_7 = { 83f86a 8bf1 0f8f71010000 83f865 0f8d82010000 } // n = 5, score = 100 // 83f86a | cmp eax, 0x6a // 8bf1 | mov esi, ecx // 0f8f71010000 | jg 0x177 // 83f865 | cmp eax, 0x65 // 0f8d82010000 | jge 0x188 $sequence_8 = { 894610 894614 894618 894620 88462c 88462d 89463c } // n = 7, score = 100 // 894610 | mov dword ptr [esi + 0x10], eax // 894614 | mov dword ptr [esi + 0x14], eax // 894618 | mov dword ptr [esi + 0x18], eax // 894620 | mov dword ptr [esi + 0x20], eax // 88462c | mov byte ptr [esi + 0x2c], al // 88462d | mov byte ptr [esi + 0x2d], al // 89463c | mov dword ptr [esi + 0x3c], eax $sequence_9 = { 57 e8???????? 59 8bf0 56 53 893e } // n = 7, score = 100 // 57 | push edi // e8???????? | // 59 | pop ecx // 8bf0 | mov esi, eax // 56 | push esi // 53 | push ebx // 893e | mov dword ptr [esi], edi condition: 7 of them and filesize < 344064 }
rule win_fatal_rat_w0 { meta: author = "AT&T Alien Labs" description = "Detects FatalRAT, unpacked malware." type = "malware" sha256 = "ec0dcfe2d8380a4bafadb3ed73b546cbf73ef78f893e32202042a5818b67ce56" reference = "https://cybersecurity.att.com/blogs/labs-research/new-sophisticated-rat-in-town-fatalrat-analysis" copyright = "Alienvault Inc. 2021" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.fatal_rat" malpedia_rule_date = "20210820" malpedia_version = "20210820" malpedia_license = "CC BY-NC-SA 4.0" malpedia_sharing = "TLP:WHITE" strings: $decrypt_func = {EC 0F B6 45 10 99 B9 AB 05 00 00 56 F7 F9 8B 75 0C 80 C2 3D 85 F6 76 0F 8B 45 08 8A 08 32 CA 02 CA 88 08 40 4E 75 F4 5E 5D C3} $s1 = "SVP7-Thread running..." $s2 = "nw_elf.dll" condition: uint16(0) == 0x5a4d and all of them }
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