Firefox: Firesheep sniffs out and steals cookies—and the account and identity of the owner in the process—of popular web sites (like Facebook and Twitter) from the browsing sessions of other users on the Wi-Fi hot spot you’re attached to.

Firesheep is a proof-of-concept Firefox extension created by Eric Butler to show how leaky the security many popular web sites (like Facebook, Flickr, Amazon.com, Dropbox, Evernote, and more) employ is. The problem, as Firesheep shockingly demonstrates, is that many web sites only encrypt your login. Once you are logged in they use an unsecured connect with a simple cookie check. Anyone from your IP address (that of the Wi-Fi hotspot) with that cookie can be you. When using Firesheep on a public hot spot any session it can intercept is displayed in the Firesheep pane with the user’s name and photograph (when available). Simply click on their name to intercept the session and start browsing the website as though you are them.

via Firesheep Sniffs Out Facebook and Other User Credentials on Wi-Fi Hotspots.