Updating and Patching Mac OS
Like all software products, bugs are found in Mac OS X after it is released. Although OS X is a very secure operating system, not patching the system means your computer is vulnerable to compromise from a less than well intentioned individual. To counter this, Apple has built automatic updating into the OS.
By default, OS X checks once a week to see if there are any patches for its software. If there are, you will automatically be prompted to install those updates. You may wish to increase the frequency of those checks, however, or check for update manually.
To access the Software Update control panel, go to Apple → System Preferences → Software Update. Increase the update frequency by clicking on the first drop-down menu and selecting daily. Manually check for software updates by clicking Check Now.
Once you are finished, simply click the red X in the upper left-hand corner to save any changes.