An example of a hacktivist is someone who breaks into a website to change it in support of the Anonymous movement.
hacktivist - Computer Definition
(HACKer acTIVIST) A person who demonstrates against a company or government agency by malicious technological means. Examples are causing a website to fail or slow down, or breaking into a computer system to obtain unauthorized information. In 2011, after MasterCard, Visa and PayPal cut off service to Wikileaks, hacktivists set up denial of service attacks against their websites. Hacktivists promote free availability of information on the Internet and may protest when actions inhibit this freedom. See hacker, Silk Road and denial of service attack.