A journalist from South Africa recently wrote to me with a series of interesting questions about forensics and I had such fun answering that I got his permission to post his questions and my answers in the last column and this one.The journalist wrote, \u201cWho\u2019s doing the computer crimes?\u201dNo one is very sure about that. There is no centralized reporting system where everyone is required to register attacks on their computers. All published research suffers from difficulties of ascertainment because of self-selection of those who respond to questions. In addition, we know from historical records that some crimes are not noticed until much later, if at all.Up until recent years, it has been a dogma in the information security field that most computer crimes (i.e., crimes against computers as targets and crimes using computers as tools) were perpetrated by employees authorized to use the systems they attacked or damaged. However, the enormous growth of the Internet has changed the views of some experts, myself included, so that we guess that we have probably crossed the boundary now and have more crimes committed by outsiders than by insiders.In general, motivations for computer crimes fall into three major categories:* Vandalism* Voyeurism* GreedWhat little research there is suggests that there is no one personality type or demographic absolutely tied to any of these categories. For example, vandals who launch denial-of-service attacks do include children with no ulterior motive, but they may also include adults attempting to extort money in a kind of modern protection racket. Similarly, there are teenagers who break into systems for fun; others are beginning to do so for-profit. Some people spreading lies on the Internet have done so simply out of free-floating ill will; however, quite a number have been involved in pump-and-dump schemes designed to drive the prices of selected stocks up or down so they could make illicit profits.\u201cHow can ordinary users protect themselves from being used as stooges for online scams?\u201dFirst\u00a0- and I hope you will stress this - don't give out confidential or private information to strangers. Don't give people who call you on the phone your bank information or your credit card numbers - no matter how convincing they sound. Don't reveal passwords to anyone: no official will ever need to know your password - they can get their work done in other ways or they can reset your password to a temporary value that will then force you to assign a new secret password that nobody else knows.Second, install an effective anti-virus program and configure it to update itself automatically every day.Third, install a personal firewall on your computer; a simple but effective free firewall is available from Zone Labs. When the firewall asks you if a program can access the Internet, answer \u201cno\u201d unless you know exactly which program it is and why it wants to reach outside your computer. Similarly, if the firewall asks you if someone can access your computer from the Internet, answer \u201cno\u201d unless there is a very good reason for saying yes and you are absolutely sure you know what you are doing.