XrayProbabiltyRatio does not disallow users from xraying, but you can check if a player is acting suspicious.
xpr.monitor xpr.stats
/xpr monitor <player> - Toggles monitoring of a player /xpr stats <player> - Shows their o/s(Ore/Stone) quota + if the quota is unnormal
This plugin will detect if a player is mining ores, in a unnormal way. The mindes ores and stones will be put into a file, along with the users name. If you do /xpr stats Notch, it will show you the stats of Notch on your Server and automatically calculate his o/s quota. Doing /xpr monitor Notch, will get you notified, everytime Notch mines a ore.
