Actor(s): Earth Lusca
A custom loader for CobaltStrike.
rule win_fishmaster_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.fishmaster." 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.fishmaster" malpedia_rule_date = "20230705" malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41" malpedia_version = "20230715" 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 = { 66c704083d00 e9???????? 48c744242001000000 ba01000000 488bcb e8???????? } // n = 6, score = 100 // 66c704083d00 | ja 0x5b9 // e9???????? | // 48c744242001000000 | dec ecx // ba01000000 | mov edx, esi // 488bcb | dec eax // e8???????? | $sequence_1 = { 488b542440 7209 488d4206 4903c1 eb12 488d4c2440 488d442446 } // n = 7, score = 100 // 488b542440 | mov ebp, dword ptr [esp + 0x98] // 7209 | mov ebp, dword ptr [esp + 0x98] // 488d4206 | inc esp // 4903c1 | mov edi, dword ptr [esp + 0x98] // eb12 | inc esp // 488d4c2440 | mov esp, dword ptr [esp + 0x98] // 488d442446 | jle 0x2b6 $sequence_2 = { 4180f82f 410f44ff c1ff02 c0e204 400afa } // n = 5, score = 100 // 4180f82f | shl dl, 2 // 410f44ff | or cl, dl // c1ff02 | dec ecx // c0e204 | mov edx, dword ptr [esi + 0x10] // 400afa | sar edi, 2 $sequence_3 = { c7450000020000 c745c000020000 c745f000020000 c745d000020000 c7451000020000 } // n = 5, score = 100 // c7450000020000 | call dword ptr [ebp - 0x68] // c745c000020000 | mov ecx, 0x3e8 // c745f000020000 | dec eax // c745d000020000 | lea eax, [ebp - 0x6c] // c7451000020000 | dec eax $sequence_4 = { e8???????? 488bd8 448b8550200000 33d2 } // n = 4, score = 100 // e8???????? | // 488bd8 | je 0xbc // 448b8550200000 | dec eax // 33d2 | lea edi, [eax + 0x27] $sequence_5 = { 724a 488b1e 488bd3 e8???????? } // n = 4, score = 100 // 724a | mov ecx, ebx // 488b1e | dec eax // 488bd3 | mov ecx, ebx // e8???????? | $sequence_6 = { 488d054d2a0000 c3 8325????????00 c3 48895c2408 55 } // n = 6, score = 100 // 488d054d2a0000 | dec eax // c3 | cmp dword ptr [esp + 0x58], 0x10 // 8325????????00 | // c3 | inc ecx // 48895c2408 | setae al // 55 | dec eax $sequence_7 = { 418d5601 33c9 ff15???????? c7855820000004000000 4489b540200000 4533c9 440fb745d4 } // n = 7, score = 100 // 418d5601 | cmp cl, 0x2b // 33c9 | jne 0x49a // ff15???????? | // c7855820000004000000 | inc esp // 4489b540200000 | mov edi, edi // 4533c9 | ja 0x4a0 // 440fb745d4 | inc esp $sequence_8 = { 4c897530 48c745380f000000 44887520 488d8580000000 49c7c0ffffffff 49ffc0 46383400 } // n = 7, score = 100 // 4c897530 | je 0x65f // 48c745380f000000 | dec eax // 44887520 | mov ecx, edx // 488d8580000000 | movzx eax, byte ptr [eax] // 49c7c0ffffffff | inc edx // 49ffc0 | mov byte ptr [ecx + ecx + 7], al // 46383400 | inc ecx $sequence_9 = { 8d71b9 eb1c 8d41d0 3c09 } // n = 4, score = 100 // 8d71b9 | lea ecx, [ebp + 0x60] // eb1c | nop // 8d41d0 | dec eax // 3c09 | lea esi, [esp + 0x58] condition: 7 of them and filesize < 812032 }
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