Mod checker

Checks what client mods a player has about two seconds after they join, and kicks or alerts staff depending on what it finds. Useful for keeping world downloaders, freecam and recording mods like Replay Mod or Flashback off your server.

How it detects mods

Two checks run together. The client's plugin channels are checked against each mod's known network channel. Then, for anything not already found that way, the plugin opens a virtual sign under the world floor (the player never sees it) with translatable text keys only that mod has in its language files. If the client has the mod installed, it fills the text in when it answers; if not, it comes back blank.

Wurst can't be caught this way, it hides its own language files. If a client rewrites the sign reply instead of answering normally, that's flagged as tampering, the kind of thing an AutoSign-style hack does.

Commands

/modcheck                              # opens the settings dialog
/modcheck on|off
/modcheck check <player>               # what was found on their last scan
/modcheck scan <player>                # scan them again right now
/modcheck whitelist <add|remove|list> [player]
/modcheck reload                       # reload settings/blocked-mods.yml

Alias /modchecker. All of it needs scriptedessentials.admin.

Ops and whitelisted players are never kicked, even with the checker on.

What happens on a hit

Each mod is set to Kick, Alert (tells staff only) or Off. A kicked player sees your configured message with the mod names filled in. An alert just logs it and messages online staff, nothing happens to the player. You can also block specific client brand strings.

Settings (settings/blocked-mods.yml)

enabled: false
alert-staff: true
kick-message: "&cPlease remove these mods to play here: &f%mods%"
blocked-brands: []
whitelist: []
mods:
  meteor-client:
    name: "Meteor Client"
    action: kick
    keys: ["key.meteor-client.open-gui"]
    channels: ["meteor-client"]

%mods% in the kick message is replaced with the comma-separated list of what was found. action per mod is kick, alert or off.

Shipped with detection for Meteor Client, Freecam, WorldTools, Bobby, Distant Horizons, Litematica, Tweakeroo, Item Scroller, MiniHUD, Accurate Block Placement, Xaero's Minimap and World Map, JourneyMap, VoxelMap, Flashback, Replay Mod, Archive World Downloader, World Downloader and Warudo Downloader. Add more mods under mods: with their own keys and channels.