Cluley is not the only security expert who has urged Apple to improve its OS protection.

In a recent interview with Computerworld Australia, Kaspersky Lab co-founder Eugene Kaspersky said the company needed to for supporting older operating systems. For example, in May this year Apple ended support for OS X 10.5, also known as Leopard, when OS X 10.7 was released.

"Apple has stopped supporting some older operating systems but there are still millions of people using these systems," he said. "It means if vulnerabilities are found, any kind of bad guys will be free to infect these machines."

Apple Australia was contacted by Computerworld Australia but declined to comment.

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