hacker

/ˈhækər/ noun [C] IT

Definition

› someone who illegally uses a computer to access information stored on another computer system or to spread a computer virus: The software company said that more than 30,000 computers were hijacked by hackers each day and used to illegally send out spam. Installing a firewall is one method of trying to protect against hackers. Hacker attacks, financial fraud, and data theft are now everyday concerns. a computer/internet hacker a criminal/malicious hacker

(Definition of hacker noun from the Cambridge Business English Dictionary © Cambridge University Press)