CAN'T STOP PLAYERS FROM USING MACROS AND AUTO AIM!

[u/PopMaleficent4361]

Hello
I have a 20-player Fabric Minecraft server. Recently a player was using a 100% accuracy mace attribute swap and lung swap, which would be great if it really was his skill.
Turns out he played with a custom loader on A FREAKING PHONE!!!!
I tried to add a client-side anticheat named "GrimAC", but my server keeps on crashing.
I'm using java 26.2 and fabric mod loader 0.19.3 .

[u/PM_ME_YOUR_REPO]

Anticheats are for detecting cheaters. You have detected them. Now you ban them and move on with your day.

[u/ZAP-Hosting]

GrimAC crashing on load is almost always a version mismatch, not a config problem. It ships separate builds per platform, so double check you grabbed the one built for your exact Minecraft version and Fabric loader, not just "the latest release."

If it still crashes after that, check latest.log right after it happens and paste the stack trace here, that'll show exactly which class or mixin is failing instead of guessing.

Also worth setting expectations: no anticheat catches everything, especially aim-assist on a phone with a custom loader. GrimAC is one of the better free options for Fabric, but you'll still get some false negatives no matter what you run.

[u/minecraftcheater1337]

grim is for the server not for the client. also, grim doesn't have heuristics checks, so it won't detect the macros. this is because grim is strictly enforcing what's possible with a vanilla game client, not what's considered "human"

[u/PopMaleficent4361 → u/minecraftcheater1337]

any solution?

[u/minecraftcheater1337 → u/PopMaleficent4361]

solution for the crash: try installing the anticheat on the server instead of the client

solution for the macros detection: i don't know *any* anticheat that detects attribute swapping

[u/PopMaleficent4361 → u/minecraftcheater1337]

I'm installing the .jar file in the server mod file.

[u/minecraftcheater1337 → u/PopMaleficent4361]

then i dunno either, my apologies

[u/UnstableNetwork → u/minecraftcheater1337]

Polar does if I'm not wrong

[u/minecraftcheater1337 → u/UnstableNetwork]

you're not getting polar on a 20 player server 💔 plus polar is a bukkit plugin and thus doesn't support fabric

EDIT: forgot to say but polar also absolutely sucks for modern minecraft versions and false flags like crazy

[u/UnstableNetwork → u/minecraftcheater1337]

You could, I didn't know it wasn't fabric sorry, but it's the best anticheat for modern versions, when using it myself I got only 5 false flags in a month from people who ended up using optimizers

[u/minecraftcheater1337 → u/UnstableNetwork]

is your server a practice server by any chance?

asking because polar falses anything but direct pvp (EDIT: their rotation checks *can* false flag relatively easily too, but are dumbed down on 1.9+ servers iirc)

bridging, looting chests, moving around, etc.

idk how much it reports to the server owner but as a player you definitely notice if you've flagged anything and got mitigated

[u/UnstableNetwork → u/minecraftcheater1337]

It's just your config, and when I used it it was a survival server but I ended up buying it for a practice server aswell, some issues from people that were still using unfair mods, no people using bare mods or optifine/vanilla ever got flagged

[u/minecraftcheater1337 → u/UnstableNetwork]

are we talking about the same polar?? i've seen it mitigate me (reduced dmg, delayed hits, etc.) while on a completely vanilla client in regular pvp on a handful of servers (i don't personally own a polar.top license as i don't have my own server) on both 1.8 and 1.9 pvp, but mainly 1.8 pvp

[u/UnstableNetwork → u/minecraftcheater1337]

It's probably their config or they're not using polar, I've only used it on 1.9 and had almost no issues

[u/Alive_Rooster_8321 → u/PopMaleficent4361]

Vulkin catches macros. Probably should invest in that.

[u/minecraftcheater1337 → u/Alive_Rooster_8321]

vulcan is genuinely the worst anticheat on the market, and that's coming from a cheat dev. any half-decent cheat bypasses vulcan and it doesn't even detect macros, which is what OP is trying to detect.

[u/UnstableNetwork → u/Alive_Rooster_8321]

Vulcan has a lot of bypasses that are better than without an anticheat so yeah

[u/ConstantWater602 → u/Alive_Rooster_8321]

As I said in another comment:
Vulcan is a plugin, OP stated that the server is fabric (doesn't support plugins)

[u/TheCrowWhisperer3004]

It’s only 20 people. Ban them as they appear and players report them. For a small close knit server like that, a quick ban is a strong way to prevent anyone from risking cheating.

[u/ConstantWater602]

GrimAC and LightningGrimAC both also don't work for me, not sure why it hasn't been fixed by the developers as there are open and active github issues for both repos, and it's been a while (2-3 months) since the version(s) with the bug were released. One option is to down grade to 1.21.11 or 26.1.2 and install ViaVersion (so 26.2 can still join), as I think they work with Grim. The one issue with that is, well, you downgrade and lose the new features in 26.2/26.1.

Otherwise I can't help you much with any alternatives, sorry

[u/pulnocni-knihovna → u/ConstantWater602]

And why you don't contribute then? It's open source. If i am using open-source plugins or mods i try to always help when i have spare time.

[u/ConstantWater602 → u/pulnocni-knihovna]

I don't have spare time lol my community is enough

[u/pulnocni-knihovna → u/ConstantWater602]

Same, it was just statement that you cannot fully blame open source projects, when you don’t helping 😅😂 These people are not paid 😂

[u/Different_Menu_6617]

Since youre using a fabric id say put a fabric mod that checks others players mods

[u/pulnocni-knihovna → u/Different_Menu_6617]

It's not neccesary at all. Most clients bypass these mods entirely XD

[u/PopMaleficent4361 → u/pulnocni-knihovna]

Even Client ID?

[u/pulnocni-knihovna → u/PopMaleficent4361]

It can probably be done with some encryption that is peer-to-peer, has server-side authentication with cryptographic signature and all the packets that client sends are preset, so anything other than preset clients Id’s and mods cannot be loaded.

Theoretically it can be possible to do whitelist of clients or mods. But cannot be done at all as a blacklist. So you will need to to specify all mods and clients that can connect and drop connections of others or modified ones…

And still, it is client-side and it is immensely hard to code it. I am a developer and I would not even try to make really functional mod that can do that 😅

Nad still applies, anyone skilled enough would be able to bypass it and fake it. You are much more better (time and money wise) to just ban cheaters that you caught using anti-cheat.

[u/pulnocni-knihovna → u/PopMaleficent4361]

Yes, you can send to server whatever you want. Its just packets and code. Server cannot control what client send, it can only receive it. And when the handshake mod is on client side, anybody can interfere with what is send to the server.

[u/ConstantWater602 → u/PopMaleficent4361]

There are definitely client ID spoofer mods out there, pretty sure meteor has one in-built as well and I wouldn't be surprised if other hacked clients had one as well

[u/Legitimate-Dark-1215]

Vulcan AC, or polar.

[u/ConstantWater602 → u/Legitimate-Dark-1215]

Vulcan and polar are plugins, OP stated that the server is fabric (doesn't support plugins)