Many people use their Macs in public environments where securing their information from prying eyes can be a top priority. Mac OS X provides several levels of security that can be used for this. Here are a few of the most basic.
The first line of defense, and one on which the other means we’ll cover hinge upon, is having a password set to secure your account. When the Mac was first set up, you were asked whether you wanted to set a password. If you ever wish to change this password, or to set one up if it wasn’t already done, click the Apple symbol on the left side of the menu bar, and choose SYSTEM PREFERENCES from the drop-down list. In the System Preferences, click USERS & GROUPS.
In Users & Groups, click CHANGE PASSWORD. You will be asked to provide the old password, then type the new password twice (once in NEW PASSWORD and once in VERIFY). You can also type a password hint to jog your memory should you ever need it. The hint is displayed if an incorrect password has been entered three times.
Your Mac might be set to automatically login to an account when it is turned on. This bypasses any set passwords, so you may wish to change this so that it boots up to a login screen. This is also done from the Users & Groups section of the System Preferences.
If the padlock icon in the lower left of the System Preferences window is locked, click it, enter your login information, and then click UNLOCK. Once the padlock is unlocked, choose LOGIN OPTIONS.
Click the drop-down list labeled AUTOMATIC LOGIN, and choose OFF.
Wake from Sleep
You can also set your Mac to require a password when waking from sleep or the screensaver. In the main area of the System Preferences, click SECURITY & PRIVACY (if you are still in the Users & Groups area, click SHOW ALL in the upper left to return to the main area first).
Make sure the GENERAL tab is selected from the tabs across the top. Unlock the padlock icon in the lower left if necessary, then click the box to the left of REQUIRE PASSWORD IMMEDIATELY AFTER SLEEP OR SCREEN SAVER BEGINS.
Once enabled, you can click IMMEDIATELY if you wish to add a buffer before requiring the password, like 5 SECONDS, 1 MINUTE, etc.
Jason Merrill, Mac & iOS Consultant