Security by Obscurity.
Windows Enthusiasts like to repeat that the only reason Macs aren’t plagued with a Windows-like security crisis is because there aren’t enough people interested in attacking Macs. With an active installed base of more than 20 million Mac users, about half of which are in the US, it does make sense for spammers to target attacks at the nearly 1,000 million Windows PCs on the planet, about a quarter of which are in the US.
The fact that Windows is a big, easy target does help the Mac platform remain unattractive to attacks. A related fact is that there are lots of ready-to-deploy malware delivery tools for Windows. Of the hundreds of thousands of known Windows viruses, there are less than 100 that are responsible for nearly all damage suffered by users. They simply keep getting reused because they work.
There are no viruses for Mac OS X. Of course, there is no magical barrier that prevents malware from being developed for Macs; it is trivial to create a Mac application or script designed to delete files or display ads. What prevents this potential from becoming a problem is that there are no easy ways to shove malware on users, install it without their knowing and in a way that is difficult to remove, and get it to automatically replicate and distribute itself.
This is easy to do on Windows. Malware installation can be automated using insecure methods Microsoft included to allow IT staff to distribute software. Once installed, malware can list itself in the byzantine Windows Registry so that it will automatically reinstall after the user tries to remove it. Poorly conceived scripting environments make it easy for viruses to replicate. Poor privilege control and unsecured network services make it easy for PCs to establish connections with other systems and propagate their infections.
