Like Lambs To The Slaughter - What Is Firesheep?

As with Advanced Evasion Techniques (AET), Firesheep has garnered significant publicity recently by rejuvenating interest in an old security problem via the creation of a slick new tool. Unlike AETs, however, the tool at the centre of this publicity storm has been released to the general public, for good or ill.

HTTP session hijacking, or "Sidejacking" as it is sometimes called, is nothing new. Papers exist discussing the technique as far back as 2004. Several applications have also been written in the past (Ferret, Hamster, Cookie Monster and FBcontroller to name a few) to take advantage of the technique. However, Eric Butler, a Seattle-based freelance software developer, has rekindled interest in the issue via the release of a simple-to-use Firefox plugin called Firesheep.

Either on its own on a Mac, or coupled with Winpcap (or Ettercap) on a PC, Firesheep can capture traffic on any unsecured wireless network to which you are connected and extract details from session cookies used by any of the web sites configured within the Firesheep application. These cookies are used by web applications such as Twitter or Facebook to register the fact that you have successfully authenticated to the host site. They do not contain your password details, but they do not need to. By using the cookie to piggyback on your unencrypted communication, the attacker running Firesheep can impersonate you and gain access to the application you are using.

It couldn't be easier to use. The attacker just fires it up, turns on packet capture, and waits for the sidebar to populate with account details it has detected on the network. He clicks on your details, and hey presto - he sees on his screen exactly what that you see on yours. And he can interact directly with the host application. He could post status updates on Twitter or Facebook on your behalf, for example. OK, that might not be too serious for some, but for those whose job it is to represent the public face of a major corporation then the potential for mischief is significant.

Should you stop using all public, unsecured wireless networks? Well, no. That would be overkill.

At the end of the day, the real solution is for providers of web applications like Facebook and Twitter to use secure connections for all their operations. In the mean time, there are a number of precautions you could, and should, take, and these (and other key points) are the subject of a research note I have just completed (subscribers only).

Don't forget to follow me on Twitter (@bwalder) to be kept informed of new research. Just don't do it from an unsecured wireless network - you never know who might be watching!