Like many scams on Facebook, the "Dislike" button succeeded because people are gullible. Here's how to not become one of those people.
Looking at Sophos' report on the Facebook "Dislike" button, which has reportedly spread virally through the social network, I noticed a pattern consistent with several other scams. Recognize these red flags, and you won't be fooled again.
First, it helps to have a pinch of skepticism when your friend posts an uncharacteristic status update. Did your old college drinking buddy just write "OMG Justin Bieber trying to flirt" on his Facebook wall? (Click on the image at left to see what to look for.) For that matter, is "OMG" out of character for your grown friends and family? A little bit of common sense always helps.
Now that you're skeptical, take a look at the Facebook status update in question. At the bottom, you'll see time elapsed since post was written and how it was delivered. So if a post comes from the web, it says "via Facebook." and if it's an update on someone's Mafia Wars progress, it says "via Mafia Wars Game."
With the "Dislike" button, the source is "The Official Dislike Button," and with another recent scam about a student attacking his teacher, the source was "Student vs Teacher." Do these messages really need their own apps for sending out messages? Facebook's "Like" button doesn't have its own app, so a genuine "Dislike" button shouldn't be using one, either.
And a video of "Worst McDs Customer" certainly shouldn't have its own delivery method for status updates, either. (Click the image at right for an example.) Questioning what comes after "via" is especially important if clicking on a link within someone's status update takes you directly to an app installation page.
Finally, some apps will give themselves away by sending you away from Facebook to an external website. The "Dislike" scam, for instance, would send people to sites such as fbdislikeit.info. This is the biggest giveaway of them all. Any time you're sent to an external website to install something on Facebook, use extreme caution and never install anything from a source you don't trust -- especially when the source claims to be "official.
The good news about this particular group of scams is that they aren't that harmful, and you can undo the damage by removing the application from Facebook's "Application Settings" page. But at that point, everyone will know you've been had.