4/15/2010
12:04 PM
George V. Hulme
George V. Hulme
Commentary

Websites Vulnerable To New Clickjacking Techniques

At Black Hat Europe, UK-based security researcher Paul Stone has demonstrated new and seemingly powerful attacks that dupe users into activating malicious links on Web sites without their even knowing it.



At Black Hat Europe, UK-based security researcher Paul Stone has demonstrated new and seemingly powerful attacks that dupe users into activating malicious links on Web sites without their even knowing it.Clickjacking simply describes a web-style cross-domain (multiple sites) attack where user initiated mouse clicks (or simply hovering over a malicious item) triggers an unintended action, such as an attack. The attack technique was first brought public by noted web security researchers Jeremiah Grossman and Robert "RSnake" Hansen in 2008.

According to Stone, a security consultant with Context Information Security in the UK, most web sites are still vulnerable to this attack-style today. And yesterday, at Black Hat Europe, Stone demonstrated other ways attackers can trick users into interacting with web pages in a way that enables the attacker to steal information.

Stone demonstrated four new clickjacking techniques such as text-field injection that could be used to target Webmail or other content rich web interactions. Despite some security precautions, browser support for the drag-and-drop API can be combined with a new attack that enables arbitrary text to be entered into a website on another domain.

Other attack techniques demonstrated by Stone include other text injection techniques; how to conduct reconnaissance on an intranet; and a way to determine if a target is logged into particular websites.

These attacks, Stone says, work in the recent versions of Internet Explorer, Firefox, Safari, and Chrome.

In his white paper, Next Generation Clickjacking, available here, Stone describes possible ways web site developers can protect against these attacks:

Frame-busting was the first technique that was recommended to counter clickjacking attacks. A page using this method will detect that is has been framed by another web site, and attempt to load itself in place of the site that is framing it (thus 'busting out' of the frame). However, a malicious site may try to use the onunload and onbeforeunload page events to prevent a framed site from navigating to a different URL.

An alternative to frame-busting is for a page to simply hide or obscure its content if it detects that it is being framed. Both Twitter and Facebook now use this approach. When framed, Twitter will hide its content and attempt to frame-bust. Facebook takes a slightly different approach by placing a semi-transparent overlay over its page, and will frame-bust when the page is clicked.

No JavaScript based method of clickjacking protection should be deemed 100 percent effective, and as a result browser vendors are now implementing declarative methods such as X-Frame-Options3, first introduced by Microsoft in Internet Explorer 8. Web browsers that support this security feature will prevent a web page being displayed in an iframe if the X-Frame-Options header is set by the page. In order to protect older browsers that do not support this feature, it is advisable for sites to use X-Frame-Options in addition to JavaScript-based methods.

Stone's white paper also goes into good, but not overly technical, detail on how the attacks work. If you're a developer, or interested in web security the paper is worth a read.

Stone always released a clickjacking tool designed to show researchers and website owners how easy these attacks may be performed on their sites. It's available here.

It's an area of web security that is as interesting as it is concerning.

For my security and technology observations throughout the day, find me on Twitter.

 

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