Don't Blame the Browser

Has the browser become a scapegoat for Web-based bugs?

Web-based vulnerabilities and attacks are on the rise. And sure, there are plenty of browser bugs (think Metasploit's Month of Browser Bugs, among other things). But there's a subtle distinction often lost amid the panic, publicity and patching: many browser-related vulnerabilities aren't actually inherent in the browser. In many cases, a vulnerability occurs because of the way the browser interacts with other applications and the operating system.

Take Internet Explorer 7's very first bug, which was reported by Secunia within hours of Microsoft releasing the long-awaited browser: Microsoft said the vulnerability wasn't technically with IE7, but with Outlook Express. IE7 was merely used as an attack vector, according to Microsoft (See New Browsers, New Bugs.)

The mhtml: issue vulnerability reported in IE6 and IE7 gives the attacker access to any Web page you access with your browser once you've visited a site he controls.

"The vulnerability is exploitable via IE7 and IE6, which would indicate that the vulnerability is likely in Outlook Express or some HTML component shared by Microsoft's Web browsers," says Sunil James, product manager for security services at Arbor Networks.

Security experts agree there's plenty of blame to go around. Browser vendors such as Microsoft allow extensions to be built into their framework, which provides attackers with an in. "It's both a browser issue and a plug-in issue. They really share the blame," says RSnake, founder of ha.ckers.org.

"The same is true with all of the header spoofing issues in Flash. It's not a problem with the browser, it's a problem with Flash, but the problem manifests itself in the browser," he says.

As for the mhtml: bug in Outlook Express, it's exploitable in IE7, which makes it a browser problem, too, James says. "Whether or not it is 'maliciously' exploitable remains to be seen," he says. "If and when public exploits arise that demonstrate nefarious activity, then I think it will really drive Microsoft to tackle the problem head-on in the context of IE7."

James says it's understandable that bug origins get blurred sometimes, especially with Microsoft software. "Microsoft applications are so intertwined with each other, as well as with the underlying Windows operating system. What results is confusion regarding where vulnerabilities actually exist," he says. "Many times, the vulnerability will be in shared code utilized by Outlook, Outlook Express, Internet Explorer, and Windows."

Either way, you can minimize your risk by keeping browser patches and antivirus, antispyware, and antispam tools up-to-date, remove any plug-ins you don’t need, such as Outlook Express, says Arbor's James. And don't click on arbitrary links, he says.

"Social engineering remains the constant with regard to how vulnerabilities such as this get exploited," he says. "In the case of your mail client, I typically don't preview emails because once you click on the link and it shows the preview, any embedded malicious code could be activated."

— Kelly Jackson Higgins, Senior Editor, Dark Reading