Teen Uses Worm to Promote Site

Using a self-propagating worm that exploits a scripting vulnerability common to most dynamic Web sites, a Los Angeles teenager made himself the most popular member of community Web site MySpace.com earlier this month. While the attack caused little damage, the technique could be used to destroy Web site data or steal private information--even from enterprise users behind protected networks, according to an Internet security firm.

The unknown 19-year-old, who used the name "Samy," put a small bit of code in his user profile on MySpace, a 32-million member site, most of whom are under age 30. Whenever Samy's profile was viewed, the code was executed in the background, adding Samy to the viewer's list of friends and writing at the bottom of their profile, "... and Samy is my hero."

"This is an attack on the users of the Web site, using the Web site itself," said Jeremiah Grossman, chief technical officer at WhiteHat Security.

The worm spread by copying itself into each user's profile. Because of MySpace's popularity--it had 9.5 billion page views in September, making it the fourth most-popular site on the Web, according to comScore Media Metrix--the worm spread quickly. On his Web site, Samy wrote that he released the worm just after midnight on October 4. Thirteen hours later, he had added more than 2500 "friends" and received another 6,400 automated requests to become friends from other users.

"It didn't take a rocket or computer scientist to figure out that it would be exponential, I just had no idea it would proliferate so quickly," Samy said in an e-mail interview posted Friday at Google Blogoscoped. "When I saw 200 friend requests after the first eight hours, I was surprised. After 2000 a few hours later, I was worried. Once it hit 200,000 in another few hours, I wasn't sure what to do but to enjoy whatever freedom I had left, so I went to Chipotle and ordered myself a burrito. I went home and it had hit 1,000,000."

Samy also received hundreds of messages from angry MySpace users. He wasn't contacted by officials from Los Angeles-based MySpace, though his account was deleted. MySpace was purchased in July by Rupert Murdoch's News Corp. for $580 million. MySpace representatives didn't return requests for comment.

Known Vulnerability

The attack depended on a long-known but little-protected vulnerability called cross-site scripting (XSS). XSS arises because many Web sites--apart from static sites that use only simple HTML code--are dynamic, allowing users to manipulate Web site source code.

Web sites and Web browsers such as Internet Explorer and Firefox try to block such XSS holes, said Grossman. But the vulnerabilities continue to exist, for which he blames both the browser creators and the Web site operators.

Standard enterprise network security tools such as firewalls, antivirus, and Secure Sockets Layer don't thwart XSS and other Web application attacks because the affected user is already behind his firewall, said Grossman, whose 14-person firm consults businesses on how to prevent such attacks.

"The network is pretty locked down. But all of the new attacks are targeting where nobody is looking--the Web application layer," he said.

Other Web application-layer break-ins include a case earlier this year where more than a hundred applicants to Harvard Business School got an early peek into their admission files by simply modifying the URL typed into their browser address box. In a more serious phishing attack last year, someone injected code into SunTrust Banks's Web site designed to send e-mail from SunTrust's Web site asking account holders for account details.

Early Example

An early version of an XSS-related vulnerability was discovered in Hotmail in 2001. That flaw allowed an attacker to send an e-mail with malformed HTML code to a Hotmail user, whose browser would interpret the broken commands as legitimate script that would tell the Web site to steal the user's private information.

Grossman said most such cases go unreported.

While both Firefox and Internet Explorer promise security enhancements in upcoming versions, Grossman said he doubts they will entirely fix the XSS problems.