Grim Anticheat

Fully async, multithreaded, predictive, open source, 3.01 reach, 1.005 timer, 0.01% speed, 99.99% antikb, "bypassable" 1.8-1.21 anticheat

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Grim Anticheat

GrimAC

GrimAC is an free open source Minecraft anticheat designed to support the latest versions of Minecraft. It currently supports minecraft versions 1.8-1.21. Geyser players are fully exempt.

This project is considered feature-complete for the 2.0 (open-source) branch. If you would like a bug fix or enhancement and cannot sponsor the work, pull requests are welcome. A premium version is planned, which will offer additional subscription-based paid checks, such as heuristics.

Installation notes

- Java 17 is now required. More information Java 17 is now required.. - Paper, Spigot, and Folia are currently supported. - If you use Geyser, place Floodgate on the backend server so grim can exempt bedrock players. Grim cannot access the Floodgate API if it is on the proxy. - If you use ViaVersion, it should be on the backend server as movement is highly dependent on client version.

Support & wiki information

- Support & discussion: Discord - Report issues: Issues - Wiki & examples: Wiki

Developer API

Grim's API allows you to integrate Grim into your own plugins. - API repository: GrimAPI - Wiki info: Wiki

How to compile

1. `git clone https://github.com/GrimAnticheat/Grim.git` 2. `cd Grim` 3. `./gradlew build` 4. The final jar will compile into the build/libs folder

Grim supremacy

What makes Grim stand out against other anticheats?

Movement Simulation Engine

* We have a 1:1 replication of the player's possible movements * This covers everything from basic walking, swimming, knockback, cobwebs, to bubble columns * It even covers riding entities from boats to pigs to striders * Built upon covering edge cases to confirm accuracy * 1.13+ clients on 1.13+ servers, 1.12- clients on 1.13+ servers, 1.13+ clients on 1.12- servers, and 1.12- clients on 1.12- servers are all supported regardless of the large technical changes between these versions. * The order of collisions depends on the client version and is correct * Accounts for minor bounding box differences between versions, for example: * Single glass panes will be a + shape for 1.7-1.8 players and * for 1.9+ players * 1.13+ clients on 1.8 servers see the + glass pane hitbox due to ViaVersion * Many other blocks have this extreme attention to detail. * Waterlogged blocks do not exist for 1.12 or below players * Blocks that do not exist in the client's version use ViaVersion's replacement block * Block data that cannot be translated to previous versions is replaced correctly * All vanilla collision boxes have been implemented

Fully asynchronous and multithreaded design

* All movement checks and the overwhelming majority of listeners run on the netty thread * The anticheat can scale to many hundreds of players, if not more * Thread safety is carefully thought out * The next core allows for this design

Full world replication

* The anticheat keeps a replica of the world for each player * The replica is created by listening to chunk data packets, block places, and block changes * On all versions, chunks are compressed to 16-64 kb per chunk using palettes * Using this cache, the anticheat can safely access the world state * Per player, the cache allows for multithreaded design * Sending players fake blocks with packets is safe and does not lead to falses * The world is recreated for each player to allow lag compensation * Client sided blocks cause no issues with packet based blocks. Block glitching does not false the anticheat.

Latency compensation

* World changes are queued until they reach the player * This means breaking blocks under a player does not false the anticheat * Everything from flying status to movement speed will be latency compensated

Inventory compensation

* The player's inventory is tracked to prevent ghost blocks at high latency, and other errors

Secure by design, not obscurity

* All systems are designed to be highly secure and mathematically impossible to bypass * For example, the prediction engine knows all possible movements and cannot be bypassed

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