This preference is to prevent easy access to your computer when the potential intruder has physical access
to it. Works in connection with screen saver. Learn more on Apple Support
Why you should enable it
You accidentally leave your computer open when you answer the door, go to the toilet, or just generally get
interrupted by something. Your roommates, classmates or just strangers can then easily access everything.
Time to fix
How to fix
Open System Preferences, click Security & Privacy, then click General.
Check Require password after sleep or screen saver.
Click the dropdown menu and choose the time. We recommend immediately, but 5 minutes is good enough