'Malicious hackers exploit software flaws - vulnerabilities in security lingo - to gain access to or control of your Mac. Apple usually releases fixes for these vulnerabilities quickly. So keeping your software up-to-date is one of the best things you can do to protect your Mac. To make sure that you have the latest software, go to the Software Update pane in System Preferences and make sure it is enabled. (By default, it is.) I recommend checking daily; sometimes attacks appear within hours of a patch release. The same is true of your anti-virus software (if you have any): keep it up to date. The major anti-virus vendors are pretty quick at updating their software's "definitions" to recognise new viruses when they appear. If you make sure you're always using the most current definitions there's every chance that by the time you read about a virus attack you're already protected.'