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 = "2023-01-25" 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 = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" 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 = { 8b45f8 83c001 8945f8 ebda 8b45f0 } // n = 5, score = 1200 // 8b45f8 | mov eax, dword ptr [ebp - 8] // 83c001 | add eax, 1 // 8945f8 | mov dword ptr [ebp - 8], eax // ebda | jmp 0xffffffdc // 8b45f0 | mov eax, dword ptr [ebp - 0x10] $sequence_1 = { 894804 8b55fc c7823410000001000000 6a10 8b450c } // n = 5, score = 1200 // 894804 | mov dword ptr [eax + 4], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] // c7823410000001000000 | mov dword ptr [edx + 0x1034], 1 // 6a10 | push 0x10 // 8b450c | mov eax, dword ptr [ebp + 0xc] $sequence_2 = { 8bec 83ec10 8b4508 8945fc 8b4dfc 894df0 8b550c } // n = 7, score = 1200 // 8bec | mov ebp, esp // 83ec10 | sub esp, 0x10 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8945fc | mov dword ptr [ebp - 4], eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 894df0 | mov dword ptr [ebp - 0x10], ecx // 8b550c | mov edx, dword ptr [ebp + 0xc] $sequence_3 = { 55 8bec 83ec10 8b4508 8945fc 8b4dfc 894df0 } // n = 7, score = 1200 // 55 | push ebp // 8bec | mov ebp, esp // 83ec10 | sub esp, 0x10 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8945fc | mov dword ptr [ebp - 4], eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 894df0 | mov dword ptr [ebp - 0x10], ecx $sequence_4 = { c7823410000001000000 6a10 8b450c 50 8b4dfc } // n = 5, score = 1200 // c7823410000001000000 | mov dword ptr [edx + 0x1034], 1 // 6a10 | push 0x10 // 8b450c | mov eax, dword ptr [ebp + 0xc] // 50 | push eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] $sequence_5 = { 740a 8b45fc 8b08 894dfc } // n = 4, score = 1200 // 740a | je 0xc // 8b45fc | mov eax, dword ptr [ebp - 4] // 8b08 | mov ecx, dword ptr [eax] // 894dfc | mov dword ptr [ebp - 4], ecx $sequence_6 = { ffd2 8b4dfc 894118 8b55fc 837a18ff 7420 8d45f8 } // n = 7, score = 1200 // ffd2 | call edx // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 894118 | mov dword ptr [ecx + 0x18], eax // 8b55fc | mov edx, dword ptr [ebp - 4] // 837a18ff | cmp dword ptr [edx + 0x18], -1 // 7420 | je 0x22 // 8d45f8 | lea eax, [ebp - 8] $sequence_7 = { 8b45fc 8b4d10 894804 8b55fc c7823410000001000000 } // n = 5, score = 1200 // 8b45fc | mov eax, dword ptr [ebp - 4] // 8b4d10 | mov ecx, dword ptr [ebp + 0x10] // 894804 | mov dword ptr [eax + 4], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] // c7823410000001000000 | mov dword ptr [edx + 0x1034], 1 $sequence_8 = { ffd1 83f8ff 7513 8b55fc 52 } // n = 5, score = 1200 // ffd1 | call ecx // 83f8ff | cmp eax, -1 // 7513 | jne 0x15 // 8b55fc | mov edx, dword ptr [ebp - 4] // 52 | push edx $sequence_9 = { 8b45f8 034510 8945f4 8b4df8 3b4df4 } // n = 5, score = 1200 // 8b45f8 | mov eax, dword ptr [ebp - 8] // 034510 | add eax, dword ptr [ebp + 0x10] // 8945f4 | mov dword ptr [ebp - 0xc], eax // 8b4df8 | mov ecx, dword ptr [ebp - 8] // 3b4df4 | cmp ecx, dword ptr [ebp - 0xc] condition: 7 of them and filesize < 81920 }
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