Apple likes to claim that Mac OS X is one of the most secure operating systems available.
While it may be true that a default install of OS X, is usually more secure than a similar default install of a consumer Linux distribution, it is also true that the average Mac OS X user is far less computer savvy than an average Linux user. A default OS X install has almost no open network ports and even secure encrypted services such as ssh have to be started manually for the first time after installation. This, in my opinion, does make OS X a much safer bet for a home user than, say, Windows or even Linux.
But, if you’re still paranoid about securing your data and would like to store all your data encrypted on your computer, OS X has ways to do that also. OS X lets you create an encrypted volume on your computer that you can use to store your data. Access to this volume is through a password and without the password all an attacker would get access to is encrypted junk.
To create an encrypted disk image, launch the Disk Utility application that is bundled with OS X and click on the New Image button. Make sure that you don’t select any volume from the sidebar when you click the New Image button as that will tell Disk Utility to create a copy of that volume instead.
Select a name and size for your new disk and from the Encryption drop down select an encryption scheme. Apple offers two encryption schemes, 128-bit AES and 256-bit AES. Choose the one that suits you. Select Read/Write Image from the image format drop down and click on the Create button.
Disk Utility will then prompt you to enter a password. You can even use a password assistant that can help you create a reasonably strong password. Store the password in your keychain, if it’s too hard to remember it.
That’s it !
Disk Utility will now create a disk image and once it’s done, it’ll be mounted for you to use it for the first time. Copy your data to this Volume and unmount it to keep it away from prying eyes. The next time you double click on the disk image, OS X will ask for a password to open it for you.