Essential Security: Fixing Common Minecraft Server Exploits

Protect your server from lag machines, packet spam, and crash exploits with these essential PaperMC configurations.

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Essential Security: Fixing Common Minecraft Server Exploits

While a DDoS attack targets your network, exploits target your server's software logic. Malicious players use "lag machines" and packet spam to freeze your TPS or even crash your server. If you are using PaperMC or one of its forks (like LeafMC), most of these can be fixed with simple configuration changes.

1. Armor Stand & Collision Lag

Attackers often use massive numbers of armor stands or crammed entities to overwhelm the physics engine.

• The Fix: In paper-world-defaults.yml, set armor-stands.tick: false and armor-stands.do-collision-entity-lookups: false.
• Entity Collisions: Set max-entity-collisions: 2 in spigot.yml to prevent entities from processing too many collision checks per tick.

2. Book & Packet Spam

"Book banning" or oversized data packets can exhaust your server's memory or crash the main thread.

• The Fix: Configure the packet-limiter in paper-global.yml. This allows you to set a maximum rate for specific packets, such as command suggestions (tab-complete) and recipe book updates.
• Join/Login Spam: Use max-joins-per-tick in paper-global.yml to prevent bots from flooding your login queue.

3. Projectile & Redstone Lag Machines

Arrows in bubble columns or complex redstone clocks can be used to "lag-lock" a server.

• The Fix: Set entity-per-chunk-save-limit for projectiles like arrow and ender_pearl to around 10. This prevents huge piles of projectiles from crashing the server during world-save/load cycles.
• Redstone: Switch your redstone-implementation to ALTERNATE_CURRENT in paper-world-defaults.yml for faster, more optimized redstone logic.

4. Map & Structure Exploits

Searching for buried treasure or following dolphins can force the server to load many ungenerated chunks simultaneously, causing severe lag spikes.

• The Fix: Disable dolphin treasure searching (mobs.dolphin.disable-treasure-searching: true) and enable find-already-discovered: true for treasure maps.

5. Neighbor Update Lag

Massive "sand fallback" machines can cause thousands of redundant block updates.

• The Fix: Paper has built-in limits for neighbor updates. Ensure your paper-world-defaults.yml has reasonable limits set for block updates to prevent these machines from freezing the tick loop.

Conclusion

Most exploits rely on "default" settings that are too generous. By tightening these limits in your configuration files, you can protect your server from the majority of common "crash" and "lag" tools without affecting legitimate gameplay.