What's that giant sucking sound? It's the noise made by your productivity swirling down the drain as you check Twitter, Facebook, Foursquare, or any of hundreds of other social-networking sites instead of getting work done, writing that essay that's due, or focusing on real life. Fred Stutzman's Anti-Social software can help.

Anti-Social disables access to over 150 social-networking sites for a period of time you specify, up to 480 minutes (8 hours). The software's Web site includes a list of blocked domains. This includes api.twitter.com, the URL used by third-party Twitter clients to access Twitter messages and account information. A reboot is required to restore access to those sites before your specified time limit has passed.

Anti-Social is a case-specific version of Stutzman's earlier utility, Freedom, which disables all network access for up to 480 minutes, optionally allowing local network access to remain available. Freedom was written for the Mac, and was recently also released for Windows XP, Vista, and Windows 7.

Stutzman is a doctoral candidate at the University of North Carolina at Chapel Hill in information and library science, and his software reflects his interest in the impact of social networking on how people make life transitions.

I interviewed Stutzman for a recent Economist article, "Stay on Target," which looks at the notion of using software to prevent yourself from doing something.

Anti-Social costs $15; Freedom is $10. Trial versions are available for each application, but include just five uses before the software is disabled.