NoDDoS

NoDDoS v6.2.9 Technical Overview

NoDDoS is a lightweight security utility for Minecraft 1.21+ designed to mitigate packet-based exploits and automated bot joins. The system uses an Atomic Sliding Window algorithm to monitor incoming traffic per-player, ensuring that rate limits cannot be bypassed by timing packets at the end of a second. It operates with high concurrency safety using ConcurrentHashMap and Atomic variables to maintain server stability during high-load events.

Core Functionality:

Packet Filtering: Specifically monitors CUSTOM_PAYLOAD, CHAT, and WINDOW_CLICK packet types.
Join Rate Limiting: Implements a two-tier threshold (Normal and Burst) to distinguish between server restarts and bot attacks.
Progressive Punishment: Increases ban duration based on the frequency of violations from a specific IP address.
Resource Efficiency: Uses asynchronous cleanup tasks and single-kick scheduling to minimize main-thread impact.

Configuration (config.yml):

settings:
  # Maximum allowed player joins per second under normal conditions
  joins-per-second: 5
  
  # Burst join limit - Reaching this triggers the progressive ban system
  burst-limit: 15
  
  # Maximum simultaneous connections allowed from a single IP address
  max-connections-per-ip: 2
  
  # Maximum packets (Chat, Click, Payload) allowed per second per player
  max-packets-per-second: 300

messages:
  prefix: "&8[&6NoDDoS&8] "
  
  # Message when the normal join limit is reached
  global-cooldown: "&cThe server is currently busy! Please wait a few seconds and try again."
  
  # Message when an IP exceeds the connection limit
  ip-limit: "&cToo many connections from this IP. Please logout from your other accounts."
  
  # Kick message for packet flooding
  packet-spam: "&cSuspicious packet traffic detected! Connection closed for security."
  
  # Message for players currently blocked by the progressive ban system
  blacklisted: "&cYour IP has been temporarily blocked due to suspicious activity. Please wait."
  
  # Message sent to admins after reloading the plugin
  reload: "&aConfiguration reloaded and violation records cleared!"

Technical Requirements:

Java 21 and Java 25
ProtocolLib dependency required for packet interception.