As mentioned in the previous post on WordPress security, I have been using WordFence as part of my security phalanx. As it turns out, this might not be a good idea for everyone.
My web hosting company recently implemented a CPU throttling protocol, presumably in order to prevent any one user in the server pool from ruining it for everyone else. I checked this morning to see what if any throttling my sites were getting, and was shocked to find that my sites were being throttled roughly four hours of each and every day on average.
I checked the current processes, but there was no information there to indicate anything was wrong (such as a process run amok). I then checked my MySQL slow query log, but this too was inconclusive, as there were a couple of processes gumming up the works sporadically, but not consistently.
So, I started disabling stuff to see what might be causing the excess resource usage. When I turned off WordFence — which runs or runs on four of the 18 sites I have on this particular host — CPU throttling instantly ceased.
WordFence is still a great tool, but if your web hosting company does CPU throttling, it might create more load on the servers than your account will permit without consequences.