JavaScript Malware Targets Intranets

Browser, beware.

There's a chilling mode of attack quietly emerging that forces an unsuspecting browser into hacking into the user's own corporate intranet. From there, the attacker can scan the network, reconfigure network devices such as routers and firewalls, or even break into corporate payroll systems.

Attackers already use this JavaScript-based malware via cross-site scripting (XSS) to attack public Websites. But Jeremiah Grossman, founder and CTO of WhiteHat Security, will demonstrate at next week's Black Hat conference in Las Vegas how this method can just as easily hack into a corporate intranet. "This is going to be very powerful stuff," says Grossman, a former information security officer at Yahoo, whose job there was to gauge the security of the company's Web applications and, according to Grossman, to "hack Websites all day."

Grossman will show how intranets, which companies don't secure as tightly as their public-facing servers, are prime targets for these JavaScript-based attacks that use XSS to exploit weaknesses in an organization's Web applications and take control of its internal network devices. "Your browser can be fully patched, but when you visit a malware site, it can take complete control of your browser and use it to fingerprint or determine what devices there are on your network, discover internal IP addresses," and even conduct corporate espionage, he says. Steering clear of "bad" Websites won't protect you either, Grossman warns. "We're told you're more likely to get attacked or 'inspected' on popular Websites rather than bottom-edge ones."

Grossman will release his proof-of-concept code for these JavaScript-based intranet attacks at Black Hat, something he regrets he didn't do at last year's conference when he showed how attackers could use XSS in phishing exploits. XSS has become a popular phishing method. "By not releasing [the XSS phishing code] it ended up helping the bad guys more because they could write it, and the good guys didn't have the code to experiment with it."

XSS isn't new, and so far it's mostly been used on public Websites, Grossman says, such as the recent XSS phishing attack on PayPal. And the recent MySpace.com worm, meanwhile, also used JavaScript malware that infected over 1 million users within 24 hours and resulted in downtime on the popular social networking site. "Hypothetically, what [the attacker] did was relatively benign compared to what he could have achieved," Grossman says. "He had access to one million users and browsers," so imagine what kind of damage he could have done if he got corporate MySpace users' browsers to attack their own internal networks.

This type of exploit lets the attacker use the browser to reach other internal and external Web servers, too. "All data that bad guys want is on a Website somewhere," Grossman says. "So they take control of your browser and make your browser download illegal content. Every log would say you or your browser had done it. That's a scary [prospect] for a corporation."

If a user happens to be logged onto the targeted Website, the attacker gains even more power, Grossman says. "For example, if the user is logged into their Web bank, the attacker can do anything the user could, such as transferring money."

Grossman says WhiteHat Security, which provides vulnerability assessment services on an outsourcing basis, has found XSS in over 1,500 custom Web apps, and that eight out of 10 Websites are infected with XSS. "Unfortunately, there is no way to patch a client to protect against it. The vulnerability is on the Website itself" within the site's custom Web applications, he says. "We need sites to start fixing these vulnerabilities."

His Black Hat demos will feature a "hacker" using XSS to deface a Web-page and for phishing with a fake page sitting on a real Website. The coup de grace, though, will be a demo using XSS and JavaScript malware to scan ports and hack devices on an internal network.

Interestingly, Grossman says the hardest part was making the attacks visible for Black Hat attendees to see it. "Doing a hack is a lot easier than an on-stage demo," he says. "It's harder to make it visible so the audience can understand it."

- Kelly Jackson Higgins, Senior Editor, Dark Reading