The exploit could snoop on unprotected Wi-Fi connections and retrieve login cookies for Twitter and Facebook, which could then be used to login to a users account and access their data. If you are using an open Wi-Fi connection, the first thing to do is to to secure your Wi-Fi connection. If you need help with it, read our earlier guides Wi-Fi Demystified I and Wi-Fi Demystified II.
BlackSheep is another Firefox add-on which is designed to combat Firesheep. BlackSheep drops fake session ID information on the wire and then monitors traffic to see if it has been hijacked. If BlackSheep finds that someone is snooping on you, it will display an alert as seen in the image above.
If you have a secure Wi-Fi connection, you have nothing to worry about, but if you don’t, the threat of Wi-Fi snooping by Firesheep is pretty high. You can circumnavigate the threat by using https instead of http while accessing the websites, but to be on the safer side, install the BlackSheep add-on too, which can be downloaded from here.
Also Read: Advice from a Wi-Fi Hacker
(Source: Life Hacker)