Having a password is highly recommended so if you haven't set one up already, you can protect your account by going into System Preferences -> Users & Groups and selecting your account. However, the issue with good security is that it all depends on you being able to set a secure password and, crucially, remembering it. What happens of you one day realize that you've forgot the password? Or more likely, what if your parents one day call you up saying they've forgot the password for their account?

There are several ways to do reset the password. The best case is if you still have access to another administrator's account. In this case you can reset the user's password by going to System Preferences -> Users & Groups. Select the account that you want to recover, click the Change Password button and type in a new password. Easy!

If you don't have access to an administrator's account, boot to the recovery partition by holding Command-R at startup (or by holding Option and selecting "Recovery HD" from the boot menu), and then selecting Terminal from the Utilities menu. When this is done and a Terminal window is open, simply type:

resetpassword

and press Return to launch the Reset Password utility. The program will launch, but do not close the Terminal window or the program will be killed as well. With the Password Reset utility now open, you can select the volume and the account, and change the password for that account.

Granted, for an operating system that is supposed to have great security, it is surprisingly simple to gain access to the computer. What if you have some top-secret files that nobody should be able to access? Is there a way to block the methods that we just described?

Of course there is! First, enable FileVault in System Preferences -> Security & Privacy. FileVault encrypts all your personal data so that even if someone manages to steal your computer they will not be able to access your data without the correct password.

You can also set a Firmware password that will be required to boot the computer and enter any of the recovery modes. This password can be set by booting to the recovery partition and selecting the Firmware Password Utility option from the Utilities menu.

After you've set the Firmware password the computer will disable all the methods we've mentioned in this article as well as several other recovery modes (reinstall, repair and so on) so do make sure that you remember the password! In a worst-case scenario you can reset the Firmware password it by opening your computer and removing one of the RAM sticks. When you boot the computer the password will be reset, after which you can replace the missing stick.