Apple has issued the fourth security update for users of Mac OS X 10.4.11 (Tiger), improving the security of (what else?) Mac OS X. The company assures us that previous such updates have also been incorporated into this last version, Security Update (2008-004), available as a free download.

"Security Update 2008-004 is recommended for all Tiger users and improves the security of Mac OS X," Apple's support page reveals. "Previous security updates have been incorporated into this security update."

To make sure that you have the latest security update on your Mac, you need to download this package and install it. You can do this using two methods:

Automatically: in the Apple Menu select Software Update and tick / check the updates you want to download and install; after selecting the items you want, click Install. Usually, you should install all available updates.

Manually: download the Security Update 2008-004 HERE and follow these steps:

1- Double click to mount the Security Update 2008-004 installer image

2- Enter an administrator account name and password when prompted and follow the on-screen instructions

3- After the installation is finished, restart the computer if a restart is required

You can repeat these steps to see if more updates are now available. However, you may be required to do it, since some software updates are prerequisites for other ones. Security Updates released for Mac OS X are usually incorporated into the next Mac OS X Software Update.

This kind of update from Apple may also be available for software released independently from Mac OS X. Software Updates are packaged so as to keep systems secure and are only offered to those that need the update. This means that if you've installed later versions that have incorporated the Security Update, you won't need to perform this update.