Cybersecurity, compliments authentication, has become the backbone of the Internet of 1 Things. In the authentication process, the word authentication is of the utmost importance as it is 2 the door through which both Mr. Right Guy and Mr. Wrong Guy can pass. It’s the key to opening 3 the most important and secure accounts worldwide. When authentication is complete, surely there 4 will be passwords. The passwords are the brain-confusing options for the user to choose when 5 making an account and during the registration/sign-up process. Graphical passwords overcome 6 the difficulties of textual passwords. This article reviews different threats to users’ passwords and 7 categorizes different authentication schemes proposed by researchers to secure password systems 8 against attacks. Standard data sets and performance evaluation measures are also studied. Finally, 9 research gaps and future directions in this essential and hot area of research are discussed.