A new firefox add-on called firesheep allows users to exploit a flaw in public wifi network. This add on was released by Mr Eric Butler according to computer world. This add-on exploits the same loophole which goggle uses for it’s Google street view cars.
With firesheep, a user can see other users who are connected using an unsecured wi-fi network. They can then go in their facebook, twitter or google account using the user’s cookie which is freely available. Users are then free to do anything to the account as though it was their own.