For several years now, computer users have had essentially one choice for navigating the Web: Internet Explorer. Despite persistent complaints about the software's security flaws, Microsoft's browser has enjoyed almost 100% market share. Enter Mozilla Firefox. Since its release last November, the open-source browser has been downloaded more than 25 million times and is well on its way to grabbing 10% of the market.

Available through the nonprofit Mozilla Foundation, which provides open-source software coded by legions of volunteer programmers, the Firefox browser offers a host of innovations, including a built-in pop-up ad blocker, tabbed browsing so users can open more than one window at a time, and a search function that seeks out a word as you type it. The program runs on both PCs and Macs, and best of all, it is free. Simply download it at, and you're ready to go. Casual Web surfers and hard-core techies alike have been quick to sing Firefox's praises, and a number of universities, including Penn State, MIT, and Yale, have begun to deploy it. But should business owners make the switch?

The main reason Firefox has taken off -- besides widespread anti-Microsoft sentiment -- is the belief that it offers a better defense against all those malicious programs out there in cyberland. Here's why: Internet Explorer is tightly woven into the Microsoft Windows operating system. That makes it more convenient to use in conjunction with other Microsoft programs like Word and Outlook. On the other hand, spyware, malware, and viruses are rampant across the digital spectrum, and the most popular points of entry are Internet Explorer and Outlook. Should one of those programs become infected, it doesn't take long for the virus to spread to your entire operating system. Secunia, a Danish security firm, for example, lists more than 20 unpatched vulnerabilities in IE 6.0.

Firefox sits on top of, rather than inside, a computer's operating system, which makes it less vulnerable. But it's not iron-clad. Already the Mozilla Foundation has reported and patched nine vulnerabilities, including a JavaScript attack capable of stealing private data and another that could illicitly copy clipboard contents.

Dean Mercado, an entrepreneur based in Holtsville, N.Y., recently installed Firefox on computers in his two businesses, the Fruitful Management Corp., a consulting firm, and Rio Enterprises, which markets pet-care products. Mercado had heard the buzz and figured he'd test-drive Firefox for consulting clients. His verdict: Firefox is indeed more secure than Internet Explorer. "Because the program is so new, Firefox is less of a target than Explorer," says Mercado. "And since it's open source, a lot of smart people are coming up with interesting extensions" -- for example, a dictionary feature that defines a word when you click on it.

There are drawbacks. While all websites work with Explorer, some do not work with Firefox. Instead, when a Firefox browser comes to visit, text and images are rendered as gobbledygook on the user's screen. That's likely to change as Firefox's growing popularity encourages developers to recode their sites. Until then, it's probably a good idea to keep two browsers ready.

Firefox might be especially attractive if you run older versions of Windows, such as Windows 98 or 2000. That's because Microsoft does not secure its older systems, instead preferring that consumers upgrade to its latest operating system, XP, which costs $99 and for which Microsoft recently released a security patch.

But security isn't everything. "I love the interface," says Ramon Ray, owner of, a consulting firm. "Firefox is easier and more efficient than IE. If your employees spend a lot of time on the Web, you should consider Firefox."