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Firesheep flames cookie capture risks

Add-on makes sidejacking simple

A developer has released a Firefox extension that illustrates just how vulnerable users of open wireless networks are when they log into websites that rely on cookies for authentication.

It is well understood that cookies sent over insecure connection can easily be captured and replayed to allow a mischief maker or hacker to log into the same website via a process called HTTP session hijacking (AKA sidejacking). A Firefox extension developed by Eric Butler dramatically illustrates this problem.

Surfers who install Firesheep can capture the credentials of anyone who happens to be using the same open network. The extension allows them, for example, to display the Facebook profile picture of a victim and the ability to then log in to a compromised account simply by double-clicking on the profile picture.

The open source extension was released on Mac OS X and Windows to coincide with a talk on the subject by Butler at the Toorcon 12 security conference.

Butler is releasing the utility in order to push more websites into using full end-to-end encryption, known on the web as HTTPS or SSL, for logins.

"It's extremely common for websites to protect your password by encrypting the initial login, but surprisingly uncommon for websites to encrypt everything else," Butler explains. "This leaves the cookie (and the user) vulnerable. HTTP session hijacking (sometimes called 'sidejacking') is when an attacker gets a hold of a user's cookie, allowing them to do anything the user can do on a particular website."

A blog post by Butler, containing screenshots of Firesheep in action, can be found here.

Until websites improve their security, a process that could take some time going by past experience, users would be well advised to use a secure VPN connection while surfing on an open WiFi network. ®

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