Hackers like to subvert computer security without permission. They are cyber criminals. This can mean gaining access to a computer across the Internet for illicit purposes. They might engage in any of the following activities:
Vandalism Destruction or digital defacement of a computer or its data for destruction's sake. Sometimes this is ego-driven. They break in and leave their mark to show they've been there.
Hacktivism A form of vandalism or electronic civil disobedience with a political agenda. Usually hacktivists have altruistic motives.
Theft Gaining access to intellectual or proprietary technology or information, sometimes for resale.
Hijacking Many of the financially motivated hackers are interested in using viruses and Trojan horses to hijack your computer so they can remotely control it for their own purposes.
Identity theft Electronic theft of personal information that can be used to steal financial resources from an individual or corporation.
Terrorism Some experts believe that terrorists will eventually launch an attack using hacking techniques.