As already announced DroidsSheep supports almost every website – also “big” webservices like facebook and Yahoo.
How does that work this simple?
There are many users that do not known that air is the transmission medium when using WiFi. Therefore information is not only transfered to its receiver but also to any other party in the network within the range of the radio waves.
Usually nothing special happens because the WiFi users discard packets that are not destined to themselves. DroidSheep does not do this. It reads all the packets looking at their contents.
Is a website sending a clear recognition feature within a message’s content, which can identify a user (“SessionID”), then DroidSheep is able to read it although it is not intended to external users. Moreover DroidSheep can use this token to use it as its own. The server can’t decide whether the authorized user or DroidSheep has sent the request.
How can I protect myself?
The only satisfying answer is: SSL respectively HTTPS.
Many providers already offer HTTPS, even facebook, however it must often be enabled in the settings first.
When using HTTPS the data are still sent to alle participants in the WiFi-network, too, but because the data has been encrypted it is impossible for DroidSheep to decrypt the contect of a message - remaining only a complete mess of letters, with which an attacker can’t do anything.
The real problem is that not every website provides SSL. What to do when you are in a public network (hotel, airport, etc.), you also want to use this and the site does not offer HTTPS though?
You can use a VPN-connection
For this the computer sets up an encrypted channel to a confidential computer which again transfers the data to the website.
This page should give a briefly overview about the problem. If you are interested in further information then it’ll possible to download my Bachelor thesis entitled “Session Hijacking on Android Devices”.