Go2Linux posted a guide about how to block, lock, or deny access to a user into Linux
If you need to block a user and do not allow him / her to log into your Linux system, maybe because she is a user who stopped working at your organization, or because she was moved to other department, or any other reason.How to block, lock, or deny access to a user into Linux
I'm going to show how to do it temporarily as to do it permanent you just need to erase the user account.