Use a pop-up blocker
Pop-up ads are not only annoying, they're also one of the ways hackers use to install spyware on your computer. Both spyware and adware are programs intended to control your computer and/or draw you to a site with the intention of obtaining your personal information. This isn't always the case with adware--it's usually just an annoying way for advertisers to draw you to their sites.

Install a spyware detector and remover
Unlike adware, spyware is a program that has the potential of obtaining your personal information. Some programs simply monitor your activities to see what you do online, in order to bombard you with spam and other types of advertising you didn't request. Although there are free anti-spyware programs online, be careful, because some of those are spyware themselves.

Avoid opening attachments from unknown sources
One of the most common ways to get a virus on your computer is to open an attachment that contains a virus. Although this can happen even when you open attachments from those you know, if they have unknowingly become infected with a virus, it's less likely than getting one from a stranger. Unless those you know have become a victim of email harvesting, meaning their contacts list has been "stolen" by a virus program, you won't be taking a risk. If you're in doubt, email the person whose name is on the email and ask if they sent you something.

Having antivirus software installed and updated constantly is essential since some viruses (very few) do not require an attachment. If you have antivirus software that checks incoming email, it will stop the virus before it can reach your inbox. Even with that in mind, don't become overconfident; new viruses are created frequently, and you're at risk until your antivirus program has a "fix" for that particular virus.

Be aware of phishing schemes
Phishing involves sending emails with links to draw the recipient to what appears to be a real site with whom they've conducted business. The most common places where this happens are Internet providers, banks, PayPal, and eBay. The email usually tells you there is something wrong with your account, and that you need to log in to fix it or your account will be closed.

Be aware, these are not real sites, but mirror sites intended only to steal your personal information. The best thing to do when you receive these kinds of email is to forward the email to the real business' fraud area, usually spoof@(whatever their domain is) and to access your account directly from your browser.

Do not click on any links unless you know it came from the provider. Also, never put your personal information in a pop up window--no reputable company or Internet provider will ask for personal information in an email, IM, or pop up window. As always, if you have any doubts, sign in to your account directly from your browser rather than click on the link; or call on the telephone to check the validity.

Never put personal information in an IM
No matter how well you know a person, even if it's your own family or friend, do not put any personal information in an IM. Of all the means of communication available online, instant messaging is one of the easiest ones for hackers to monitor. This is also true of forums and personal Web sites. If you need to give someone an address or telephone number, go to private email, which is more secure since it is protected by your antivirus program and firewall. NEVER put your credit card information in an IM or email, and try to deal with sites that allow you to store your information rather than putting it in whenever you buy something.

Change your password routinely
If you do online banking or shopping, change your password on a regular basis so that if anyone does manage to get your password, they won't have the correct one. If you even suspect you may have been hacked, change all of your passwords to any accounts you think may be affected.

Although these tips will not prevent you from being a victim of Internet fraud, they will certainly lessen the possibility. The important thing to remember is to protect your private information by maintaining security on your computer and exercising caution when giving out personal information.

David Gewirtz is the author of How To Save Jobs and Where Have All The Emails Gone? For more than 20 years, he has analyzed current, historical, and emerging issues relating to technology, competitiveness, and policy. David is the Editor-in-Chief of the ZATZ magazines, is the Cyberterrorism Advisor for the International Association for Counterterrorism and Security Professionals, and is a member of the instructional faculty at the University of California, Berkeley extension. He can be reached at david@zatz.com and you can follow him at http://www.twitter.com/DavidGewirtz.