MyBB Community Forums

I have been noticing for the last several weeks that I have been getting the same type of hits into my site preceded by a hit from search engines. I know they are after the ebooks I have stored for my members, because that is the search terms used. What I don't know is, this any thing to worry about. it looks like this.
simplesurvival.us/forums/misc.php?action=proxy

So what do you all think?

Do you by any chance have the Proxy Killer plugin by labrocca?? That adds an action=proxy

Yes I do come to think about it. So does that mean I am safe. If they would just take the time to read all they have to do is sign up to the forums and make a few post and all the survival ebooks I have on the site is theirs to download free.