I'm a Mac. You're a PC. But we both need antivirus software.

Apple, which has long perpetuated the belief that its operating system is immune to security problems, is recommending that users install security software to make it harder for hackers to target its platform.

"Apple encourages the widespread use of multiple antivirus utilities so that virus programmers have more than one application to circumvent, thus making the whole virus writing process more difficult," according to a support note posted last month.

Apple's position -- while prudent -- undercuts its popular advertising campaign which anthropomorphized PCs running Windows as an overweight nerdy man with the flu.

But data by computer security researchers has shown that while Apple hasn't been affected by malicious software nearly to the extent as Windows, it's merely because hackers go after the most widely used platform.

Apple is gaining market share, however, which means hackers could increasingly look to exploit the platform, particularly if it becomes perceived as an easier target.

In the past, Apple has been slow to patch, according to researchers from the Swiss Federal Institute of Technology. They released a study in March looking at so-called zero-day vulnerabilities, when a security problem is publicly disclosed without a patch.

That measure is important since it means users are unprotected during the time it takes to create, test and then apply a patch. The study concluded Apple often had more unpatched vulnerabilties than Microsoft.

Apple systems are also not immune from problems in third-party software, such as plug-ins, which are used to view animated Flash graphics and PDF (Portable Document Format) files.

Security problems in plug-ins have frequently been manipulated to cause browsers to redirect to malicious Web sites, which are rigged to try and take advantage of browser flaws.

Compared to Windows, there aren't nearly as many antivirus products for Apple computers. Russian security vendor Kaspersky Lab, however, said earlier this year that it has a prototype Apple version of its software that it could publish in days depending on market demand. Symantec, McAfee and Intego offer Apple antivirus products as well.

Sophos, based in Abingdon, England, currently sells an enterprise-level product for OS X, and interest has been increasing in the product, said Graham Cluley, senior technology consultant.

Analysts in the company's labs have seen more financially motivated malicious software for OS X, Cluley said. Last week, the company spotted "OSX/Jahlav-A," a Trojan downloader.

Jahlav is often planted on Web sites as a purported key generator that can be used to figure out valid product codes for hacked software. But if it is installed, a hacker has complete control over the Apple computer and can download other bad software to the machine to steal data, Cluley said.