Wall Street Journal tech columnist Walter S. Mossberg is fond of saying that Macintosh users don’t need antivirus software. For example, in today’s column about “craplet” software on new PCs, he writes,

“An excellent way to avoid or minimize the craplet problem is to simply buy an Apple Macintosh computer. New Macs don’t have any craplets displayed on their desktops. On a new Mac, no third-party software is automatically launched when you start the computer, and you don’t need antivirus or antispyware programs because the Mac is essentially free from those menaces.”

I agree with Mossberg that antivirus software isn’t needed for the Mac today. Nevertheless, I run antivirus software on my Apple MacBook laptop. I’ve also recommended to my father that he run antivirus software on the Mac Mini that he has at his home.

I run antivirus software on a computer that doesn’t need it to protect myself against a legal risk, not a technical one, since I use my Mac for Web banking. There is a risk to Web banking, of course. One of those risks is that somebody will get your password and drain your account. These days, many brokerage firms that offer Web banking have some kind of guarantee in which they promise that they will reimburse you for any money lost as a result of unauthorized transactions. But there is a hitch: they will only reimburse you if you are running antivirus on your computer.

For example, Schwab’s privacy policy (revised July 1, 2006) states that customers should keep their computer and browser software current with security updates, install and update antivirus and antispyware software, and use a personal firewall. Apple’s Mac OS has a built-in firewall, but it doesn’t have built-in antivirus or antispyware software. So if you were using Schwab and lost money for some reason, Schwab wouldn’t have to honor its guarantee if you were not running antivirus. My brokerage company has a similar policy.

This policy is not just for Web banking. One of the organizations where I work demands that I have antivirus installed on my computer before I put that computer on the company’s local area network (LAN). Not having antivirus installed is a security offense.

What’s truly ironic here is that the antivirus programs on the Mac spend most of their time looking for PC viruses, not Mac viruses. That’s because, as Mossberg points out, there are few, if any, actively rampaging viruses that affect Mac users. It’s tempting to think that this is because the Mac is a superior operating system, but it’s really just because the Mac is the minority. If Apple ever gets popular–really popular–then we’re sure to see spyware and viruses on the Mac, just as we see them on other computer platforms.

Indeed, I have seen spyware-like programs on the Mac before. A few years ago, my wife had her Mac’s Web browser loaded up with toolbars and other “helpful” programs that monitored every website she visited and sent this information back to a few large corporations in California that used them for marketing purposes. Such programs are widely available today. Download them onto your Mac, and you, too, can have a Mac that’s filled with spyware.