URL Parsing Bug in IE Invites Phishing Attacks

By Larry Seltzer  |  Posted 2004-06-11 Print this article Print

The bug, which affects fully patched versions of IE, lets malicious sites assume the privileges of more trusted zones.

A bug in fully patched versions of Microsofts Internet Explorer Web browser allows violations of the browsers security zones, with the result that an unknown malicious site could assume the privileges of more trusted zones. Researchers on several security mailing lists have been discussing the bug since yesterday and appear still to be learning about it.

The same vulnerability could be used for phishing attacks, in which the URL in the address bar appears to be for one site but is in fact a link to a different site. Both of these problems rely on certain misconfigurations of the DNS and Web server on the malicious Web site.

For insights on security coverage around the Web, check out eWEEK.com Security Center Editor Larry Seltzers Weblog.
The malformed URL contains text on the left side—which may or may not be a valid address—the actual domain on the right and a particular syntax in between. If the domain on the right-hand side of the URL is properly misconfigured, the browser will go to that site and put it in the zone belonging to the site on the left. If an arbitrary name is used on the left, the site is put in the local intranet zone, which has less restrictive privileges than the default Internet zone.

There are many mitigating factors to this problem. Attacks involving malicious Web sites are usually exploited via throwaway, free Web site services that allow a certain amount of anonymity on behalf of the attacker. But this attack requires control of the DNS and Web server configuration, so the attacker would have more difficulty remaining anonymous. The phishing aspect of it is arguably more of a problem concerning the DNS configuration of the target site.

Microsoft said it is investigating the matter and will take appropriate actions.

Check out eWEEK.coms Security Center at http://security.eweek.com for the latest security news, reviews and analysis.

Be sure to add our eWEEK.com developer and Web services news feed to your RSS newsreader or My Yahoo page

Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

Submit a Comment

Loading Comments...
Manage your Newsletters: Login   Register My Newsletters

Rocket Fuel