A. A lot of Mac users are in for a shock. The idea that Macs are invulnerable to viruses is an old one. Unfortunately, it isn't true.
That isn't to say viruses are common on Macs. Historically, there have been very few Mac viruses. Meanwhile, there have been tens of thousands on Windows.
However, that was mostly a function of market share. Until recently, Windows was used by over 90 percent of the market. Macs, on the other hand, made up less than 10 percent. In 2007, for example, it was around 6 percent.
That isn't the case anymore. Macs now comprise 16 percent of the U.S. market, and that number is increasing. That's enough for virus writers to start taking notice.
A major virus for the Mac was recently discovered. It's called MacDefender. You can learn more about it here.