Updating to a newer version of mac os x
Worse, when users run Apple's Software Update program, it misleadingly tells them "Your software is up to date." Lest you think that nobody would bother releasing malware to attack such old systems, in recent years malware has been found in the wild that was designed to attack multiple platforms, and occasionally this malware has contained Power PC native code.
This didn't just happen once; it has happened again and again.
However, some Macs are still limited to Lion (version 10.7.5), which is evidently no longer getting security patches now that Yosemite has been released; the lack of a Lion version of the recent Security Update 2014-005 is a harbinger of things (not) to come.
In recent history, Apple has only patched operating system vulnerabilities for the current and two previous versions of OS X.
Although Microsoft publicly announces its support timetables for Windows, and the Ubuntu Linux company Canonical does likewise, Apple has never given any official word to the public regarding how long each version of Mac OS X or i OS will continue to receive security updates, and Apple consistently ignores press inquiries about when levels of support will be dropped for its operating systems.
Remember, even Lion isn't supported anymore, and Snow Leopard hasn't gotten new security updates for quite a while, so it's best to avoid using both of these older operating systems.
Like last year with the release of Mavericks, Apple chose to continue supporting all the same Macs as the previous release of the operating system.
This means that if your Mac was compatible with Mavericks or even its predecessor Mountain Lion, you'll be able to upgrade to Yosemite.
This makes non-upgraded Macs a potentially significant target for criminals interested in infecting large numbers of computers.
Anyone still using Lion, Snow Leopard, or an earlier version of Mac OS X should strongly consider upgrading to Yosemite if their Mac supports it, or if not, they should buy new hardware if they can afford it.You may, however, still be able to buy it by calling 1-800-MY-APPLE; in the past, Apple would send a special code via e-mail that would enable Lion to be downloaded from the Mac App Store.