Secure your Mac by Updating it

The process is the same for Leopard and Snow Leopard. Click the Apple logo at the top of the screen. Select System Preferences and then click Software Update. You want your Mac to check for and download updates automatically. Make sure the boxes labeled "Check for updates" and "Download updates automatically" are checked. Then click Check Now to check for updates manually. Your Mac will check for new software. Recommended updates will be displayed. If it finds updates, click Install. You may need to reboot the computer after installing

One update may lead to others. When you've installed all available updates, a message will notify you. Operating system updates often plug security holes. PC owners know this very well as Windows is updated weekly.