What Is a Hacker?

The word hacker has come to refer to a computer user who trespasses on computer systems for fun or profit. The growth of the Internet has created unlimited opportunity for these intruders to steal secrets, tinker with Web sites, abscond with credit card information, or just generally make mischief. Computer hackers have also spawned a whole new mythology. They are celebrated for their skill and daring.

Some ascribe lofty artistic and political motives to these bandwidth banditos. But the professionals who install and maintain computer networks are not impressed with computer hackers.

This hour explores some of the techniques hackers use to gain control of computer systems. As you study these techniques, you'll notice that many of the concepts are built around fundamental properties of TCP/IP that you learned about in earlier hours. The next hour explores some of the security techniques used to keep intruders off the network.

The Internet literature is full of vague psycho-profiles of who the hacker is and what the hacker thinks. Much of this information is based on anecdotes and speculation. However, there is general agreement that computer attackers tend to fall within the following broad categories:

• Adolescent amateurs These are kids who are really just playing around. The so-called script kiddies often have only a rudimentary knowledge of computer systems and primarily just apply intrusion scripts and techniques available on the Internet.

• Recreational hackers This category of adult intruders encompasses a broad range of motivations. Most are in it purely for the intellectual challenge. Some want to make a statement against a particular industry or organization, and others are disgruntled former employees.

• Professionals This relatively small but very dangerous group consists of experienced experts who know a lot about computers. They are very hard to trace because they know all the tricks. In fact, they invented some of the tricks. These intruders are in the game strictly for the financial reward, but they wouldn't have gotten where they are if they didn't love what they do.

It is impossible to describe all the various scams and tricks used by intruders to gain access to computer systems. This hour is intended only as an introduction to some important techniques. As you read through the techniques described in this hour, remember the most important rule of computer security: If you think you've secured your network, think again. Someone out there is spending a lot of time and effort trying to find a new way in.

By the Way

To many, a hacker is simply a high-end user who is obsessed with and devoted to working with computers whether or not that user has any malicious intent. Many of these high-end users are proud to call themselves hackers and object to the use of the word hacker for Internet burglars and vandals. These users prefer to use the word cracker for cyber vandals. Unfortunately, one cannot easily restrain a word from finding its definition. The term hacker is now widely applied to computer intruders, and the verb to hack is commonly used for Internet attacks. We can sympathize with high-end good guys who want a label that is more romantic than power user, but unfortunately they'll have to share the term. Waylon Jennings, after all, called himself an outlaw but never robbed a bank.