server backdoor!

Hello all.  I have a quick question.  I am currently setting up a linux bukkit server owned by someone else, mostly via putty and filezilla.  I am supposed to receive a profits percentage from said server.  However, in the event that they scam me upon it's completion, what would be the best way of going about setting up a hidden backdoor?  I just want to be able to kind of have a nuke option so they can't profit from my work.

netcat listen on port 666 to execute... i feel like that's gonna get noticed.  i mean if i try to run anything, they could just type top and bam its on the cpu usage.

And yes.  I mean I guess they wouldn't notice long enough for a script to just delete the folder.  i'm gonna have to double check how (if ever) they do their backups.  that or write a world file corrupting script.