No X-ray is a Minecraft Bukkit server plugin that aims to end any form of x-raying being possible.
- Base protection - obfuscate whole rooms with naturally occuring underground blocks
- Entity proximity hiding - entities are hidden depending on how far away the player is from them
- Player LOS hiding - players must have non-occluding line of sight to see each other
On large servers I imagine that a lot of performance optimisations would be necessary. If you think you can lend a hand, feel free to help out!