Researcher shows new clickjacking methods

A computer security researcher has released a new browser-based tool that can be used to experiment with next-generation "clickjacking" attacks along with details of the four new techniques.

Clickjacking is a style of attack where a user is tricked into clicking on certain parts of a Web page with hidden buttons that perform malicious actions. The hidden buttons are delivered by an invisible iframe, which is a window that brings other content into the target Web site.

Clickjacking become well-known in 2008 after researchers Robert Hansen and Jeremiah Grossman discovered a kind of attack involving Adobe Systems' Flash application that could give remote access to a victim's Web camera and microphone.

Since that time, many Web sites and browser makers have taken steps to shore up their defenses, but the vast majority of sites are not protected, said Paul Stone, a security consultant with Context Information Security in the U.K. He revealed four new kinds of clickjacking attacks on Wednesday at the Black Hat conference that are effective against most Web sites and browsers.

Stone showed one demonstration that used the drag-and-drop API (application programming interface) implemented in all browsers. With some social engineering, users can be tricked into dragging an item on a Web page, which would cause text to be inserted into fields.

"There are many things that this could be used for," Stone said. "You could send fake e-mails from a user's account. You could also edit documents in some kind of document-editing system."

Stone also showed a content-extraction clickjacking attack, which could be used to steal tokens that are used to authenticate a session and guard against CSRF (cross-site request forgery) attacks. In a CSRF attack, a Web application is tricked into honoring a request from a malicious Web site.

Stone has developed a tool that developers can use to try out the new clickjacking techniques. It is available for download on his company's Web site.

The tool is a point-and-click browser-based application. It has a "visible" replay mode to see how exactly a particular attack works and also a "hidden" mode that shows the attack from the victim's perspective. The tool is in beta and works with Firefox 3.6, although Stone said they are working on compatibility with other browsers.

Stone recently discovered two browser-specific clickjacking vulnerabilities, one in Internet Explorer and one in Firefox, which have both been patched. Browser makers have also been implementing ways to guard against clickjacking.

Internet Explorer 8, Safari version 4 and higher and Chrome version 2 and higher now recognize an HTTP header called X-Frame-Options. As long as a Web page is tagged with that, the browsers will prevent the Web site from being rendered within a frame, which clickjacking requires. Mozilla is planning to have the feature in a future version of Firefox.

Web sites can also use JavaScript to obscure or hide content and also prevent a page from being displayed in an iframe. Facebook and Twitter use JavaScript, but do not use X-Frame-Options, according to Stone. Using JavaScript, however, is not completely effective.

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