What is firewall & what it does?

A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system. If an incoming packet of information is flagged by the filters, it is not allowed through. If you have read the article How Web Servers Work, then you know a good bit about how data moves on the Internet, and you can easily see how a firewall helps protect computers inside a large company. Let's say that you work at a company with 500 employees. The company will therefore have hundreds of computers that all have network cards connecting them together. In addition, the company will have one or more connections to the Internet through something like T1 or T3 lines. Without a firewall in place, all of those hundreds of computers are directly accessible to anyone on the Internet.

What is a zombie computer?

Imagine that the Internet is a city. It would undoubtedly be the most remarkable & diverse city on the planet, but it would also be incredibly seedy & dangerous. You could find the world's most comprehensive libraries there alongside X-rated theaters. Inside this city, you would also discover that not everyone is who they seem to be - even yourself. You might find out that you've been misbehaving, although you don't remember it. Like the unwitting agent in. "The Manchurian Candidate", you discover you've been doing someone else's bidding & you have no idea how to stop it. A zombie computer is very much like the agent in "The Manchurian Candidate". A hacker secretly infiltrates an unsuspecting victim's computer & uses it to conduct illegal activities. The user generally remains unaware that his computer has been taken over - he can still use it, thought it might slow considerably. As his computer begins to either send out massive amounts of spam or attack Web pages, he becomes the focal point for any investigations involving his computer's suspicious activities.

Where computer virus came from?

Computer viruses are called viruses because they share some of the trails of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person. Unlike a cell, a virus has no way to reproduce by itself. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive.

A computer virus shares some of these trails. A computer virus must piggyback on top of some other program or document in order to launch. Once it is running, it can infect other programs or documents. Obviously, the analogy between computer & biological viruses stretches things a bit, but there are enough similarities that the name sticks. People write computer viruses. A person has to write the code, test it to make sure it spreads properly and then release it. A person also desingns the virus's attack phase, whether it's a sily message or the destruction of a hard disk.

Who are the famous hackers?

Steve Jobs and Steve Wozniak, founders of Apple Computers, are both hackers. Some of their early exploits even resemble of some questionable activities of some malicious hackers. However, both Jobs & Wozniak outgrew their malicious behavior and began concentrating on creating computer hardware & software. Their efforts helped usher in the age of the personal computer - before Apple, computer systems remained the property of large corporations, too expensive & cumbersome for average consumers.

Linux Torvalds, creator of Linux, is another famous honest hacker. His open source operating system (OS) is very popular with other hackers. He has helped promote the concept of open source software, showing that when you open information up to everyone, you can reap amazing benefits. Richard Stallman, also known as 'rms' founded the GNU Project, a free operating system. He promotes the concept of free software & computer access. He works with organizations like the Free Software Foundation (FSF) & opposes policies like Digital Rights Management.

On the other end of the spectrum are the black hats of the hacking world. At the age of 16, Jonathan James became the first juvenile hacker to get send to prison. He committed computer intrusions on some very high-profile victims, including NASA & a Defense Threat Reduction Agency server. Online, Jonathan used the nickname (called a handle) "comrade". Originally sentenced to house arrest, James was sent to prison when he violated parole.