Shortly after we came back from our big vacation overseas in May, my Apple (NASDAQ:AAPL) PowerBook was hit with a computer virus. I can't tell you which one, but it was enough to cripple my Microsoft (NASDAQ:MSFT) Office for the Mac software. Symantec's (NASDAQ:SYMC) Norton Anti-Virus found the bug, and then eradicated it by exterminating my entire in-box. (Thanks, guys.)

Fortunately, I only lost a month's worth of e-mail because I back up my data to an external hard drive. But I've learned my lesson. I now back up my data a whole lot more, although still probably not as often as I should.

Indeed, viruses are spreading. There are more than 90,000 classes of computer viruses out there, according to Sophos, a maker of anti-virus software. No wonder researcher Meta Group says that it expects 12% of information technology budgets to be spent on securing computer systems over the next couple of years. With the Department of Commerce estimating $872 billion in gross domestic product from IT last year, services, hardware, and software for security could eclipse $100 billion in 2004 and continue growing steadily.

So you can go ahead and color me unsurprised to hear yesterday that anti-virus software maker McAfee (NYSE:MFE) acquired privately held Foundstone for $86 million in cash. McAfee is one of the two acknowledged heavyweights in virus-crushing software, with Symantec being the other. Foundstone will add to McAfee's portfolio by providing software that shows businesses where their networks are vulnerable to outside attack, a high-value service that will likely continue to deliver healthy margins. (Foundstone says it has more than 400 customers, including AT&T (NYSE:T), McKesson (NYSE:MCK), and Motorola (NYSE:MOT).)

The deal is the latest in a spree of acquisitions in tech security lately -- even Time Warner's (NYSE:TWX) AOL unit recently got in on the game. AOL's move followed on the heels of Microsoft and Motley Fool Stock Advisor pick Dell (NASDAQ:DELL) signaling their intent to fight the good fight against digital bugs.

But yesterday's news interested investors because it shows that McAfee is intent on continuing its recent momentum by buying to complete its product portfolio. Trading at roughly 20 times its expected forward earnings, and 15 times its free cash flow when compared to its enterprise value, McAfee shares are anything but cheap at today's prices. Strong growth delivered from acquisitions such as the Foundstone deal could change that in a hurry.

For more Fool coverage of the virus wars, check out these articles from Alyce Lomax:

Both Dell and Time Warner have been part of the market-beating returns for subscribers of Motley Fool Stock Advisor. A risk-free six-month trial is yours for the asking.

Fool contributor Tim Beyers still thinks the Mac is much more insulated against viruses than those pesky Windows PCs, but he also thinks you can never be too careful. Tim owns no shares in any of the companies mentioned, and you can view his Fool profile here.