A firewall can also be set to prevent unauthorized data, such as a company's proprietary information, from being sent out over the Internet from a user's computer. Hacktivists might deface child pornography Web sites, or post messages about policies or governments they oppose. Political hacks have been targeted against the governments of India, Israel, China, and the United States , among other countries. A burglar alarm for a computer or network that tells an administrator when an intruder might be trying to gain access to the system. They also give administrators data to help them track any intruders who successfully enter a system.
Hackers use the term to describe obtaining total control over a system.
More experienced hackers tend to disdain script kiddies, because the script kiddies often don't understand the technology behind the attacks they launch. Often arriving via e-mail as an attachment, Trojans are far more sophisticated than viruses or worms, and often allow a hacker unlimited access to a compromised machine. Three of the most common Trojan horses are Back Orifice, NetBus, and SubSeven. A hacker who is motivated to explore systems for intellectual curiosity, rather than for malicious or criminal intent. White hat hackers oppose doing damage to systems, stealing data, or interrupting service to a Web site.