In common parlance the term hacker can be used to describe a
person who illegally gains access to and sometimes tampers with information in a computer system
I wold like to know what term should be used to describe the opposite, namely someone who defends against a hacker to prevent the hacker from achieving her/his goal.
A Computer Security Specialist. From chron.com:
What Does a Computer Security Specialist Do?
Computer security is of utmost importance to company managers responsible for protecting their company’s information assets. Computer security specialists, or information security analysts, are responsible for protecting those assets on a day-to-day basis. A computer specialist’s job is to make sure only authorized people gain access to confidential information.
Opposite of a hacker is a user. Someone who follows the rules and doesn't explore the system.
