Locking your screen when you get up from your desk is a security action that is often overlooked and can have dangerous consequences. Failing to lock your screen can open you up to several vulnerabilities--some more serious than others.
Although many organizations have a policy which automatically locks your screen with a screen saver after a certain amount of inactivity, not all screen savers are password-protected, leaving your workstation defenseless.
Here are a few actions the bad guys can do when you leave your workstation unlocked and unattended:
Press the Windows key + the L key at the same time on your keyboard.
Press and hold Ctrl+Alt+Del and then choose Lock This Computer.
For Mac:
If using Mac OS X (2015 and later), be sure to enable the lock screen ability. Find this under System Preferences > Security & Privacy > and look for the "Require password..." setting under the General tab.
Then, press Control+Command+Q on your keyboard, or do a quick web search to learn the keyboard shortcut for your Mac's Operating System.
Set up hot corners, which allows you to push your cursor to a certain corner of your screen to lock the computer. This can be set up under System Preferences > Desktop & Screen Saver then choosing Hot Corners.
Get in the habit of locking your screen. If nothing else, it will prevent coworkers from sending prank emails from your account!