hacker
noun [ C ]
IT uk/ˈhækər/ ussomeone who uses a computer to access information stored on another computer system without permission, 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