Bear in mind that from April to December 2011 there were only 58 attempted security threats to the Mac - a mere fraction compared to Windows malware:
Why not read the user tips linked to in this thread by me and Thomas instead of repeatedly asking the same question?
Bear in mind that from April to December 2011 there were only 58 attempted security threats to the Mac
Note that F-Secure is counting individual variants separately with that number, which is why it's so much higher than my number. By my count, there were 5 individual malware programs that appeared during that timeframe, but some, at least, came in many different variants. For example, I consider all MacDefender variants to be the same malware, because they all behaved the same way and were made by the same hackers. However, due to frequent name changes (MacSecurity, MacProtector, MacGuard and MacShield) and other changes to the code and packaging - which were meant to sneak the malware past anti-virus software, and which were highly effective at doing so - there were many different variants of MacDefender.