The PlayStation Network is a social gaming hub that connects PlayStation 4 users together. The network allows you to chat with other users, make new friends, and play online games. The PlayStation Network also implements a couple of features to help you protect your privacy and block unwanted users. Turn on your PlayStation 4 and sign-in to your local account. Tap on the Up button (D-pad) to move to the Function menu and then select Friends.

Type the name of the user you want to block in the Find Player on PSN field and tap on the X button to launch a search. Once done, select the Ellipsis button displayed next to the username > Block.

The selected user will be added to your block list in Friends > Players Blocked.