The Database security is always one of the major tasks for all the Database Administrators.
I have also prepared one article to create Read only User in PostgreSQL.

PostgreSQL: Script to Create a Read-Only Database User

In this post, I am sharing small note about REVOKE privileges for newly created Database Users of PostgreSQL.

Before a few days ago, one of the PostgreSQL Junior DBA asked this question on my FB Page. He created one new DB User in PostgreSQL and without giving a any permission that USER can CONNECT to all Databases.

Yes: When you create any new DB User in PostgreSQL, It has a default CONNECT privileges.
But It cannot access any Table or data of Databases, yes It can create new Table in any Database.

To prevent a new User for connecting any existing Database, we should run REVOKE command on particular User or Role.

REVOKE CONNECT privileges from Database:

REVOKE CONNECT ON DATABASE Database_Name FROM User_Name;

REVOKE all privileges from Database:

REVOKE ALL PRIVILEGES ON DATABASE Database_Name FROM User_Name;

You should GRANT only required Databases:

GRANT CONNECT ON DATABASE Database_Name TO User_Name;