CoreProtect is a plugin for post-lookup of griefers or Xrayers. With this plugin installed it is very easy to log any blocks being placed or broken and an area can even be rolled back to restore it's original or how it was before a specific time. This is a big problem for Xrayers because even after wekks if your tunnels get found or an admin looks up diamond ores broken and finds yours it can be looked up who it was, when and it can be rolled back. Of course you are gonna get banned after that...