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 = "2023-07-11" 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 = "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 = { 8b4dfc 83c101 894dfc ebe7 8b4508 8be5 } // n = 6, score = 1200 // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 83c101 | add ecx, 1 // 894dfc | mov dword ptr [ebp - 4], ecx // ebe7 | jmp 0xffffffe9 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8be5 | mov esp, ebp $sequence_1 = { 8b45fc c60000 8b4dfc 83c101 894dfc ebe7 } // n = 6, score = 1200 // 8b45fc | mov eax, dword ptr [ebp - 4] // c60000 | mov byte ptr [eax], 0 // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 83c101 | add ecx, 1 // 894dfc | mov dword ptr [ebp - 4], ecx // ebe7 | jmp 0xffffffe9 $sequence_2 = { 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_3 = { 034510 8945f4 8b4df8 3b4df4 741e 8b55fc 8b45f8 } // n = 7, score = 1200 // 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] // 741e | je 0x20 // 8b55fc | mov edx, dword ptr [ebp - 4] // 8b45f8 | mov eax, dword ptr [ebp - 8] $sequence_4 = { 8b4508 8945f8 8b4d0c 894df4 837df400 7507 } // n = 6, score = 1200 // 8b4508 | mov eax, dword ptr [ebp + 8] // 8945f8 | mov dword ptr [ebp - 8], eax // 8b4d0c | mov ecx, dword ptr [ebp + 0xc] // 894df4 | mov dword ptr [ebp - 0xc], ecx // 837df400 | cmp dword ptr [ebp - 0xc], 0 // 7507 | jne 9 $sequence_5 = { 837a18ff 7420 8d45f8 50 687e660480 8b4dfc } // n = 6, score = 1200 // 837a18ff | cmp dword ptr [edx + 0x18], -1 // 7420 | je 0x22 // 8d45f8 | lea eax, [ebp - 8] // 50 | push eax // 687e660480 | push 0x8004667e // 8b4dfc | mov ecx, dword ptr [ebp - 4] $sequence_6 = { 83ec0c 8b4508 8945f8 8b4d0c 894df4 837df400 7507 } // n = 7, score = 1200 // 83ec0c | sub esp, 0xc // 8b4508 | mov eax, dword ptr [ebp + 8] // 8945f8 | mov dword ptr [ebp - 8], eax // 8b4d0c | mov ecx, dword ptr [ebp + 0xc] // 894df4 | mov dword ptr [ebp - 0xc], ecx // 837df400 | cmp dword ptr [ebp - 0xc], 0 // 7507 | jne 9 $sequence_7 = { ffd0 8b4dfc c7411c01000000 8b55fc 8b45f4 } // n = 5, score = 1200 // ffd0 | call eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // c7411c01000000 | mov dword ptr [ecx + 0x1c], 1 // 8b55fc | mov edx, dword ptr [ebp - 4] // 8b45f4 | mov eax, dword ptr [ebp - 0xc] $sequence_8 = { 034d0c 894df8 8b55fc 3b55f8 7411 8b45fc } // n = 6, score = 1200 // 034d0c | add ecx, dword ptr [ebp + 0xc] // 894df8 | mov dword ptr [ebp - 8], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] // 3b55f8 | cmp edx, dword ptr [ebp - 8] // 7411 | je 0x13 // 8b45fc | mov eax, dword ptr [ebp - 4] $sequence_9 = { 890a 8b55fc 8b02 8945fc } // n = 4, score = 1200 // 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 condition: 7 of them and filesize < 81920 }
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