New security research is shining a light on an attack technique that can be used to trick users into entering their personal information on phishing sites.
The attack, dubbed tabnapping, was uncovered by Aza Raskin, creative lead for Mozilla Firefox, and affects all the major browsers on Windows and Mac OS X.
Raskin's proof-of-concept attack takes advantage of users who keep multiple tabs open. If the user visits a malicious site or one that has been compromised, the attacker can silently change the contents and label of an open, inactive tab to resemble the log-in screen of another site, such as Google Gmail.
Raskin demonstrated the attack on his blog. If visitors open another tab and then go back to the blog, they will see the blog page has changed to a fake Gmail log-in screen.
"Using my CSS history miner you can detect which site a visitor uses and then attack that site (although this is no longer possible in Firefox betas)," Raskin wrote. "For example, you can detect if a visitor is a Facebook user, Citibank user, Twitter user, etc., and then switch the page to the appropriate log-in screen and favicon on demand.
"Even more deviously, there are various methods [one can use] to know whether a user is currently logged into a service. These methods range from timing attacks on image loads, to seeing where errors occur when you load an HTML Web page in a script tag ... You can make this attack even more effective by changing the copy: Instead of having just a log-in screen, you can mention that the session has timed out and the user needs to reauthenticate. This happens often on bank Websites, which makes them even more susceptible to this kind of attack."
Jerry Bryant, group manager for security response communications at Microsoft, said users should always check to make sure the Lock icon is present in the address bar before entering personal information on any Website, and check that the URL of the site is correct. Internet Explorer 8's SmartScreen filter, which offers some protection against suspected and known phishing sites, can help mitigate the attack, he added.
Raskin indicated the Firefox Account Manager Mozilla is working on for the next version of the browser mitigates the attack.
"User names and passwords are not a secure method of doing authentication; it's time for the browser to take a more active role in being your smart user agent; one that knows who you are and keeps your identity, information and credentials safe," he wrote.