A "trojan" has been found which affects Macintosh computers
A company called Intego has discovered a trojan called "PokerGame" available for download on some web sites which, if downloaded and installed in a Macintosh computer, attempts to take control of that Macintosh computer for harmful purposes. It might, for example, record your bank passwords and email them to a criminal. Unfortunately others will create other trojans using the same methods. (In other words, in a few months, you could find a trojan called BestRecipesEver.)
What to do?
Do not download any programs unless you are sure that the source is a reliable one.
For those who want to dig into the subject: