Need some research help

I've been invited to give a lecture about the writing process, and I want to touch on procrastination busters. I've seen a few people talk within the last year or two about installing software that will temporarily block Internet access, either entirely or just to certain sites like Facebook, as a way to keep themselves from getting distracted when they're supposed to be writing. I think this program gives you the option of either setting a time limit or entering a password to turn off the block. But I can't remember what it's called, and search results aren't bringing up anything that sounds familiar! Have you heard of such a program, or more than one?