Full disk encryption is primarily useful for protecting a stolen Mac. When your drive is unlocked, files on it can be read. However, before it's unlocked (ie, your Mac is shut down), all data on the drive will be scrambled. This prevents data recovery by unauthorized third parties, who might try to access it using Target Disk mode on your Mac or by removing your Mac's hard drive and attaching it to another computer.
If you use numerous online services regularly then you will (or should) have different credentials for each one. These may be difficult to remember. Often people store their credentials in a text, Word, or Pages file for easy access, but this is a highly insecure way to store passwords. In OS X you have a built-in alternative for managing passwords called the keychain.
Unlike other security options, the keychain is enabled by default to store your various passwords for online services, email accounts, sharing services, and many other authentication routines. Whenever you see a checkbox for saving your password, or in a drop-down menu when using Safari, this is OS X asking you to store these passwords in an encrypted file called the login keychain.
This keychain can be managed using the Keychain Access utility (/Applications/Utilities). In most cases, unless you're troubleshooting your Mac, there's little need to use this utility. Instead, simply use the option to save your passwords and OS X will automatically enter them where appropriate.
There are some third-party password tools such as 1Password that provide expanded password management. If Keychain Access and Safari's ability to store passwords don't provide you with the features you need, try 1Password or a similar utility.
Locking and locating
A final couple of options for protecting your Mac include securing your computer when you have to leave it unattended and enabling remote access to it — not only to interact with it from afar, but also to track and lock it down, if needed.
You set up the first of these options in the General tab of the Security & Privacy system preference. Just enable the Require Password option and choose Immediately or 5 seconds from the pop-up menu and you'll be required to enter a password to use your Mac after it's gone to sleep or the screen saver has started. The shorter the time interval you use in this feature, the better, especially for laptops. Just close the lid to lock the system.
To remotely access and track your Mac, open the iCloud system preference and switch on the Back to My Mac and Find My Mac iCloud services. With the first option checked you can access the sharing services you've enabled on your Mac. For example, with Screen Sharing turned on, your remote Mac will appear in the Finder sidebar, where you can click it and share its screen to view and interact with your remote Mac's desktop.
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