Systems that appear to be running an unannounced next-generation version of Apple's Mac OS X operating system have begun to appear in online tracking logs.

In the last few weeks, AppleInsider has seen more than 30 total visits from machines listed as running OS X 10.9. A handful of machines running Intel-based OS X 10.9 Macs have also been sighted elsewhere on the Web.

While such information can be faked, the growing number of appearances of systems claiming to run OS X 10.9 could indicate that Apple is already testing early betas of the next major update to its Mac operating system.

For the last couple of years, Apple has been upgrading OS X on an annual basis. The latest version, OS X 10.8 Mountain Lion, debuted on the Mac App Store in July, and OS X 10.7 Lion launched in July of 2011.

Prior to that, OS X 10.6 Snow Leopard launched in August of 2009, while OS X 10.5 Leopard saw its initial release in October of 2007.