EFF

The Web is an insecure place and getting more insecure all the time. The latest threat, the Firesheep add-in for Firefox, is particularly dangerous because it is exceedingly simple to use. Someone with absolutely no hacking experience can grab your private login information to sites such as Facebook and Amazon, and then log in as you and do anything they want, as if they were you. The free Firefox add-in HTTPS Everywhere helps protect against that threat and other privacy invaders by effectively encrypting information when you visit certain Web sites.