NEW YORK (CNN/Money) - Maybe e-mails should start to come with a Surgeon General's warning:

Opening the following attachment may be hazardous to your health because your friends and co-workers will want to beat you senseless for unwittingly turning into a source of endless spam.

Yup. E-mail viruses and worms continue to plague computer users. Several variants of viruses, such as MyDoom, Bagle and NetSky, have made headlines this year. And last year was a rough one as well, with the dreaded SoBig virus and Blaster worm wreaking havoc.

But all this has been good news for Symantec, the world's leading developer of anti-virus software for consumers. Shares of Symantec (SYMC: Research, Estimates) are up nearly 16 percent year to date and 46 percent in the past six months.

Despite this solid run, several fund managers and analysts still think there's room for more upside ahead for Symantec, which is holding an analyst meeting Wednesday afternoon.

One reason to remain bullish is that the issue of security is not going to go away anytime soon.

"There's going to continue to be a problem with viruses and worms," said John Rutledge, manager of the Evergreen Technology fund. "Symantec is like the companies who make door locks. There are always burglars out there." Symantec is the largest holding in Rutledge's fund.

And Symantec bulls love the diversification of its business. In its fiscal third quarter, 51 percent of sales came from corporate customers and 49 percent came from its consumer business.

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The heavy focus on consumers -- Symantec sells the Norton brand of anti-virus software -- is key, said Robert Mattson, an analyst with Gartmore Global Investments, which owns Symantec in several mutual funds. Mattson said that consumer anti-virus is a great market to be in because it is one of the few areas of the software market where a company has pricing power.

"Symantec has been able to keep raising rates on the consumer side," said Mattson. "People feel that they have to have it."

That's especially true because consumers don't have tech staffs to turn to when their PC is infected. Sean Jackson, an analyst with Avondale Partners, said that as more consumers switch to high-speed broadband connections at home, they would probably be even more willing to spend on anti-virus software to protect their computers. (Jackson doesn't own the stock and his firm has no banking relationship with Symantec.)

And as corporations start to spend more on tech, that should help Symantec as well. In addition to anti-virus software, Symantec sells firewall protection software and other types of network security products. Plus, Symantec's model of charging a monthly fee leads to a steady stream of recurring revenues, said Carl Marker, manager of the IMS Capital Value fund, which owns the stock.

Security for wireless devices represents a strong growth opportunity for Symantec on the consumer and corporate side as well. To that end, Symantec announced earlier this week that it will be working with cell phone market leader Nokia on security solutions for Nokia's new 9500 Communicator, a phone/e-mail device geared toward corporate customers.

Of course, Symantec is not the only game in town. Network Associates (NET: Research, Estimates) is another leading anti-virus software developer. And it also has seen a sharp rise in its stock lately: shares are up 13 percent this year and 30 percent in the past six months.

But several fund managers said they prefer Symantec because of its heavier consumer presence. Less than a quarter of Network Associates' revenues in the fourth quarter were from sales of the consumer version of its McAfee anti-virus software.

In addition, Network Associates has been faced with several accounting problems and earnings disappointments in recent years. So Symantec is viewed as, pardon the pun, the safer security software bet.

"Symantec historically has outperformed Network Associates. Network Associates is not a bad company but I'm much more of a believer in Symantec's business," said Michael Cuggino, president of Pacific Heights Asset Management, which owns Symantec in the Permanent Portfolio fund.

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But Symantec's success comes at a price, however. The stock is not cheap, trading at about 30 times estimates for Symantec's next fiscal year, which ends in March 2005. Still, analysts are predicting that earnings will increase 17 percent next year and at that rate for the next few years.

"It's definitely pricey but people are willing to pay up for a company with well defined growth prospects," Cuggino said. "There are few companies out there that can command a multiple higher than other stocks because of their history of execution."

Marker, who has owned the stock since early 1999, agrees.

"The P/E is reasonable for a software company that's growing at the rate that Symantec is," Marker said. "If anything, I think that their business is going to strengthen as time goes by."