I’ve learned something new this week about Internet security and privacy. Web bugs. Also known as web beacons. If you already know about them, you’re wondering what rock I’ve been living under. If you don’t know about them, listen up.

Web bugs are tiny, transparent 1 × 1 pixel objects that advertisers or other snoopy corporate entities embed on web pages or in emails to track your browsing activities, preferences, etc. Web bugs are the things that tell spammers you’ve opened their email, that indeed there is someone using that address who apparently has some interest in what the email is pitching. The companies that gather this information share it with or sell it to other companies, and all sorts of information about you goes flying around the Internet without your permission or knowledge.

Facebook lost a lawsuit last year for using web bugs, and supposedly has stopped using them. But just about everyone else out there does, it seems. Blizzard Entertainment caused a big uproar just last month with a deal involving sharing their users’ real names with Facebook. (Why does Facebook seem to turn up every time I read anything about Internet privacy?) I have better things to do with my time than examine the source code of every email I receive and every web page I land on, looking for bugs, and besides, the damage has already been done.

Fortunately, Firefox offers an add-on called Ghostery, a nifty little app that blocks web bugs. Better yet, it tells you which ones are lurking on each page. If you enable it, a little list of crossed-out bug sources pops up whenever you land on a bugged page. (Even WordPress stats work off a bug, it seems; if Ghostery messes that up, I can whitelist WP.) It’s very satisfying to see those names with lines through them, and know you’ve struck another tiny blow for personal privacy.