A security researcher has discovered a means of hijacking sensitive information from cookies in Internet Explorer. The 'cookiejacking' technique could expose credentials from Facebook, Twitter, Gmail, or other online services, but Microsoft doesn't consider it a serious threat. So, is the sky falling, is the security researcher crying wolf, or is the real risk somewhere in between.
Security researcher Rosario Valotta recently demonstrated the 'cookiejacking' technique, and has details of the attack on his blog. The 'cookiejacking' threat, and underlying zero-day flaw affect all versions of Internet Explorer running on any version of Windows, so the pool of potential victims is significant.
What Is a Cookie?
A cookie is a small text file used by a Web browser or application to store information like site preferences, or user account credentials for site authentication.
What Is 'Cookiejacking'?
The technique exploits a flaw that bypasses the Security Zone protection in Internet Explorer to enable the attacker to capture the contents of cookies that should not be exposed.
What Is at Risk?
Most text files contain text that would of little value. But, if you are logged in to a site like Facebook, Twitter, or Gmail, cookies are used to store user account information needed to authenticate so you don't have to log in repeatedly. If an attacker can hijack these cookies, they could impersonate you or access sensitive data within the affected site or service.
Is It a Serious Threat?
The attack is not trivial to pull off. The actual 'cookiejacking' is just one piece of a larger puzzle that requires different attack techniques, and duping the user into becoming a willing participant.
Microsoft's Jerry Bryant downplayed the threat based on the complexity of the attack and the level of user interaction required for it to work. "In order to possibly be impacted a user must visit a malicious website, be convinced to click and drag items around the page and the attacker would need to target a cookie from the website that the user was already logged into."
While all of that is true, though, many users click the little checkbox that says "keep me logged in" so they don't have to enter user credentials every time they visit a site like Facebook, and it is actually fairly simple to lure users into clicking. Valotta created a Facebook game where users undress a naked woman by clicking on her clothing to remove it. Voila! A game like that would definitely get users clicking.
What Should You Do?
So, the sky is not falling. Successfully executing a 'cookiejacking' attack to extract sensitive credentials does take a fair amount of user interaction, and hopefully informed users know enough not to chase that rabbit down the hole.
At the same time, Valotta is not crying wolf. The 'cookiejacking' technique does work with a little cooperation from the user, and with more than 500 million users on Facebook playing all sorts of silly games, it is not a stretch to think that a significant number of users could be socially engineered to fall for the attack.
Microsoft does not consider the 'cookiejacking' issue to be a big enough threat to warrant an urgent, out-of-band security update for Internet Explorer, but it is allegedly working on a fix that will be available over the next few months. In the meantime, exercise some caution with a little extra common sense, and don't go clicking on things just because someone asks you to.