Blocking Malicious URLs

By Larry Seltzer  |  Posted 2003-08-05 Print this article Print

Malicious URLs can open a server to many kinds of attacks, and the tools to protect your site aren't always helpful or easy to use.

Many years ago, Tim Berners-Lee, father of the World Wide Web, spoke at a conference. His message was that URLs that users could decipher were a bad idea. Web applications should employ URLs that are deliberately complex—black boxes for which only the Web server has a key. That way, programmers could ensure and control the user experience.

This makes sense from a security perspective as well: Apart from exposing the underlying logic of Web applications in a way that invites exploits like SQL injection, easily apprehended URLs facilitate attacks based on legal but malicious HTTP requests designed to break a server. Many exploits on many Web servers—most often Microsoft IIS—have been based on URLs that were technically legal but employed buffer overflows or similar techniques.

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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.

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