I have gotten reports that people were griefed in the darklands. Aparently someone with a Xray plugin is going hunting for chests. Please understand that I am not able to track that. The plugin I have alerts me when people are mining ores and not when they are opening chests. If you want to protect your chests, then place an ore on the 6 spots around it so that anyone who opens a chest has to dig through ore before being able to open it.
All I can do is check if the people going for the chests also have mined normal ores with Xray and ban them for that.