Project Zomboid: Solving "Malformed Packet Detected"
The "Malformed Packet Detected" error is the most common reason for players being kicked from modded Project Zomboid servers. Despite the scary name, it rarely indicates actual cheating. Instead, it's usually a false positive triggered by a mod performing a calculation (like heavy inventory sorting or vehicle physics) faster or differently than the built-in Anti-Cheat expects.
1. The Anti-Cheat Logic
Project Zomboid has 24 separate Anti-Cheat protection types. Each one monitors a specific action (Movement, Inventory, Health, etc.). Modded items often trip these "logic checks."
2. False Positives
High-latency players or those using overhaul mods (like Brita's or Filibuster Rhymes' Vehicles) are significantly more likely to trigger packet errors during heavy server load.
3. The Permanent Fix
To ensure a smooth experience for your community, you must selectively disable the specific Anti-Cheat types that are clashing with your mod list.
How to Disable Anti-Cheat Protections
- Navigate to your Supercraft Panel and Stop the server.
- Open the File Manager and go to
/Zomboid/Server/. - Edit your
server_settings.inifile. - Scroll down to the section marked AntiCheatProtectionType. These are numbered 1 through 24.
AntiCheatProtectionType1=true AntiCheatProtectionType2=true ... - Change the value of the problematic types to
false.- The "Nuke" Option: If you are running 50+ mods, many admins set all 24 types to false to prevent any further issues.
- Click Save and Restart the server.
The Most Common Problematic Protections
| Anti-Cheat Type | Triggered By... | Solution |
|---|---|---|
| Type 12 & 13 | Inventory movement and sorting mods. | Set to false for any modded server. |
| Type 21 | Vehicle mods and "Physics" fixes. | High priority to disable if players are kicked while driving. |
| Type 24 | Large containers and weight-reducing backpacks. | Essential for any mod introducing 100+ capacity bags. |
Note for Build 42: The new Liquid and Component systems in Build 42 have added additional packet complexity. If you are experiencing kicks after the update, double-check that AntiCheatProtectionType12 is disabled, as it handles the new crafting interactions.
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