Most powerful bot filtering solution for Minecraft proxies. Built with LimboAPI.
Modrinth
Описание и обсуждение на русском языке (spigotmc.ru)
Описание и обсуждение на русском языке (rubukkit.org)

Test server: ely.su

• LimboAuth - Auth System built in virtual server (Limbo). Uses BCrypt, has TOTP 2FA feature. Supports literally any database due to OrmLite.
• LimboAPI - Library for sending players to virtual servers (called limbo)

• Highly customizable CAPTCHA's - change fonts, backplates, colors, alphabet-pattern, length;
• Client settings and brand checking;
• Highly customisable config - you can change all the messages the plugin sends;
• Ability to partially disable protection on low-loads of proxy;
• Ability to prepare raw packets to reduce CPU usage;
• Fast MCEdit/StructureBlock schematic world loading for CAPTCHA checking;
• And more...

• limbofilter.commands.sendfilter | /sendfilter - Send Player to Filter Command
• limbofilter.admin.stats | /lfilter stats - Plugin Statistics Command
• limbofilter.admin.reload | /lfilter reload - Reload Plugin Command
• limbofilter.admin.* - Gives All Admin Permissions

Test server: i7-3770 (4c/8t 3.4GHz) Dedicated server, Ubuntu Server 20.04, OpenJDK 11, 16GB DDR3 1600MHz RAM, 4GB RAM is allocated to proxy.
Attack: Motd + Join bot attack (100k joins per seconds, 1.17 Protocol)

Your donations are really appreciated. Donations wallets/links/cards:

• MasterCard Debit Card (Tinkoff Bank): 5536 9140 0599 1975
• Qiwi Wallet: PFORG or this link
• YooMoney Wallet: 4100 1721 8467 044 or this link
• Monero (XMR): 86VQyCz68ApebfFgrzRFAuYLdvd3qG8iT9RHcru9moQkJR9W2Q89Gt3ecFQcFu6wncGwGJsMS9E8Bfr9brztBNbX7Q2rfYS