If you're using Mac OS X Lion or Mountain Lion, then you have access to Mac OS X's Gatekeeper security feature. Gatekeeper is the newest addition to OS X's security arsenal and it wants to help keep your system free of malware and malicious code.

While Gatekeeper is a great new security feature, it's not without its own problems, one of which could leave you scratching your head when you attempt to install a new app and receive a strange error that you've never seen before.

In this article, we'll show you how to get the most out of Gatekeeper and avoid errors installing non-gatekeeper-approved software as well.

What does Mac OS X's Gatekeeper do?

Think of the Gatekeeper security feature as the doorman behind the velvet rope at an exclusive club, where the club is your Mac, and the people in line are legitimate software applications and malware applications trying to get in.

The doorman at the club probably has a list of people that are pre-approved for entry or are VIP guests. The Mac Gatekeeper feature also has a list that it checks potential entrants against as well. Gatekeeper's "Allow Applications Downloaded From" setting has three options: "Mac App Store", "Mac App Store and Identified Developers", and "Anywhere".

When you try to install new software, the Gatekeeper feature checks to see what the above setting is and decides whether or not to let the software run on your computer.

The theory is that applications in The Mac App Store and those created by Apple Identified Developers play by Apple's rules with regards to security and are likely to present less of a threat than just any old app that you download from an unknown source on the Internet.

Identified Developers also digitally sign their code which helps gatekeeper screen out malware.

How do I access Gatekeeper's settings?

1. Click the "System Preferences" icon from the dock menu or the Apple menu.

2. Click on the "Security and Privacy" icon from the "Personal" section of the System Preferences window.

3. Click the lock icon at the bottom of the screen and enter your password if required.

4. Click on the "General" button near the top of the window.

5. Look for the section that says "Allow Applications Downloaded From". This is where the Gatekeeper settings are located. You can change the setting if needed to allow certain programs downloaded from sources other than the Mac App Store or from Apple Identified Developers. Please note that changing this to "Anywhere" effectively turns off the Gatekeeper protection feature.

What is the "Damaged Software" Error and how do I get around it to install an app that is not Gatekeeper-approved?

When trying to install a software package on your mac from the Internet, you may receive an error that says "APPLICATION_NAME is damaged and can't be open. You should move it to the trash." This error is caused by the OS X Gatekeeper blocking settings. In order to install an app that is not a Mac App Store download or an app that wasn't developed by a Apple identified developer, you will need to perform the following:.

1. Follow the steps mentioned above for accessing the Gatekeeper settings.

2. Change the "Allow Applications Downloaded From" setting from its current value to "Anywhere".

3. MAKE SURE that the app you are trying to install is free of malware by scanning it with an anti-malware scanner prior to continuing.

4. Attempt to install the app that generated the error message.

5. After you have installed and run the app for the first time, go back to the "Allow Application Downloaded from" settings area and change it from "Anywhere" to either one of the other two settings (Mac App Store being preferred as the stronger security setting).