Lethic is a spambot dating back to 2008. It is known to be distributing low-level pharmaceutical spam.
rule win_lethic_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.lethic." 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.lethic" 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 = { 837df400 7507 33c0 e9???????? 8b55f4 8b4218 } // n = 6, score = 1200 // 837df400 | cmp dword ptr [ebp - 0xc], 0 // 7507 | jne 9 // 33c0 | xor eax, eax // e9???????? | // 8b55f4 | mov edx, dword ptr [ebp - 0xc] // 8b4218 | mov eax, dword ptr [edx + 0x18] $sequence_1 = { 33c0 e9???????? 8b45fc 8b4d10 894804 } // n = 5, score = 1200 // 33c0 | xor eax, eax // e9???????? | // 8b45fc | mov eax, dword ptr [ebp - 4] // 8b4d10 | mov ecx, dword ptr [ebp + 0x10] // 894804 | mov dword ptr [eax + 4], ecx $sequence_2 = { 50 8b4dfc 83c108 51 8b55f4 } // n = 5, score = 1200 // 50 | push eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 83c108 | add ecx, 8 // 51 | push ecx // 8b55f4 | mov edx, dword ptr [ebp - 0xc] $sequence_3 = { 8b45fc 8b08 894dfc ebec 8b55fc } // n = 5, score = 1200 // 8b45fc | mov eax, dword ptr [ebp - 4] // 8b08 | mov ecx, dword ptr [eax] // 894dfc | mov dword ptr [ebp - 4], ecx // ebec | jmp 0xffffffee // 8b55fc | mov edx, dword ptr [ebp - 4] $sequence_4 = { eb42 6a10 8b55fc 83c208 52 } // n = 5, score = 1200 // eb42 | jmp 0x44 // 6a10 | push 0x10 // 8b55fc | mov edx, dword ptr [ebp - 4] // 83c208 | add edx, 8 // 52 | push edx $sequence_5 = { ebec 8b55fc 8b45f4 8b08 890a 8b55fc } // n = 6, score = 1200 // ebec | jmp 0xffffffee // 8b55fc | mov edx, dword ptr [ebp - 4] // 8b45f4 | mov eax, dword ptr [ebp - 0xc] // 8b08 | mov ecx, dword ptr [eax] // 890a | mov dword ptr [edx], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] $sequence_6 = { 8945fc c745f801000000 837dfc00 7507 33c0 e9???????? 8b45fc } // n = 7, score = 1200 // 8945fc | mov dword ptr [ebp - 4], eax // c745f801000000 | mov dword ptr [ebp - 8], 1 // 837dfc00 | cmp dword ptr [ebp - 4], 0 // 7507 | jne 9 // 33c0 | xor eax, eax // e9???????? | // 8b45fc | mov eax, dword ptr [ebp - 4] $sequence_7 = { 3b55f8 7411 8b45fc c60000 } // n = 4, score = 1200 // 3b55f8 | cmp edx, dword ptr [ebp - 8] // 7411 | je 0x13 // 8b45fc | mov eax, dword ptr [ebp - 4] // c60000 | mov byte ptr [eax], 0 $sequence_8 = { 8b08 890a 8b55fc 8b02 8945fc 8b4df4 51 } // n = 7, score = 1200 // 8b08 | mov ecx, dword ptr [eax] // 890a | mov dword ptr [edx], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] // 8b02 | mov eax, dword ptr [edx] // 8945fc | mov dword ptr [ebp - 4], eax // 8b4df4 | mov ecx, dword ptr [ebp - 0xc] // 51 | push ecx $sequence_9 = { eb42 6a10 8b55fc 83c208 52 8b45fc 8b4818 } // n = 7, score = 1200 // eb42 | jmp 0x44 // 6a10 | push 0x10 // 8b55fc | mov edx, dword ptr [ebp - 4] // 83c208 | add edx, 8 // 52 | push edx // 8b45fc | mov eax, dword ptr [ebp - 4] // 8b4818 | mov ecx, dword ptr [eax + 0x18] condition: 7 of them and filesize < 81920 }
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