SAN FRANCISCO -- Apple replaced advice on Wednesday that people install anti-virus software on Macintosh computers with assurances that the machines are safe "out of the box."

The move prompted online speculation as to whether Apple was merely polishing the Macintosh image or that the increasingly popular computers are as impervious to hackers as the California company maintains.

Apple routinely touts how rarely Macintosh computers are afflicted with malicious software as compared to machines based on Microsoft Windows operating systems, which run more than 90 percent of the computers in the world.

On Tuesday Apple removed a 2007 Knowledge Base posting telling people to install "multiple anti-virus utilities" in Macintosh computers to thwart ill-willed software savants with arrays of defenses.

"We removed the Knowledge Base article because it was old and inaccurate," Apple spokeswoman Monica Sarkar said Wednesday.

"The Mac is designed with built-in technologies that provide protections against malicious software and security threats right out of the box."

Some software specialists believe that Macintosh computers have been spared attacks mostly because hackers see more return in targeting Windows-based machines that make up the bulk of the market.

Macintosh sales have rocketed with the popularity of Apple's iPhones and iPods, but the rising profile of the computers has also made them more appealing to hackers.

Software security firms consistently urge people to protect computers with anti-virus software kept up-to-date no matter the operating systems used.

"Since no system can be 100 percent immune for every threat, running anti-virus software may offer additional protection," Sarkar said.