2006 had all the makings of a landmark year for Mac OS security. The first OS X viruses surfaced in the wild, gaping security holes were revealed, and analysts gave dire warnings about the possibilities for a security epidemic.

And all of this was among a group of users famous for seldom needing any security software at all.

As the year came to a close, however, the epidemic that would infect thousands of systems and strike fear into the hearts of Mac users everywhere had yet to materialise.

Malware authors had largely ignored the Mac in favour of the much larger and easily controlled pools of unpatched Windows systems.

Viruses failed to spread substantially in the wild, and the occasional Apple update did enough to keep most Mac users secure.

The year started off with the discovery of a virus that would become the first of many predicted 'wake-up calls' for Mac users in 2006.

The Leap-A virus first appeared in February disguised as a collection of photos of Apple's upcoming Leopard operating system labelled 'latestpics.tgz'. Experts soon diagnosed the file as the first verified Mac OS X virus. 

Leap-A, which used Apple's iChat software, spread via social engineering, and the user had to be tricked into giving permission for the installation.

The virus had no intentional adverse effect on a host machine, although an error in the code could prevent infected applications from running.

While Leap-A posed little threat of spreading widely or causing any damage, security experts claimed that it would act as a warning salvo to Mac users and convince them that security threats did exist for the Mac OS.

"Some owners of Mac computers have held the belief that Mac OS X is incapable of harbouring computer viruses, but Leap-A will leave them shell-shocked as it shows that the malware threat on Mac OS X is real," predicted Sophos senior technology consultant Graham Cluley when the Leap-A reports first surfaced.

By March, however, fewer than 50 Leap-A infections had been recorded by Symantec and the idea that 'Macs don't get viruses' remained strong, even in the eyes of Apple.