"You are sending me spam email," I recently wrote to one of my customers. Of course, he had no idea he had sent me an email promoting assorted "enhancement" products, but, nonetheless, that's what happened.

He also had no idea he had sent the same email to everyone in his contacts list. I knew that he had, though, because right there in the "To" field of the message were the email addresses of everyone in his contacts list.

I've seen the same thing happen to three other customers during the past month. The messages were different, but the symptoms were the same; unbeknownst to them, they were sending spam email messages to everyone in their contacts list.

There are three ways this can happen to you: your email account has been hacked, your computer is infected with a virus known as a "spambot," or, your email address has gotten on some bad guys' list and he is sending out spam email masquerading as you.

Spambots (as in, "spam-sending robots") are nothing new; they've been around for years. They enter your computer the same ways as other viruses, either through infected emails or attachments, infected instant messages, infected "apps" found on social networking sites like Facebook, infected fake programs that you download and install, or infected links and ads found on websites. You can even get what's known as a "drive-by infection," where your computer gets infected merely by looking at an infected website.

Spambots can be dealt with like any other virus, with antivirus products and scans being the most popular solutions. It is also important to update your computer's operating system. This applies to Apple Macintosh computers as well as Windows PCs. Anyone who tells you that Apple Macs can't get viruses needs serious reeducating.

Keep in mind, though, that no single antivirus product can catch all of the viruses, trojans, rootkits and worms that are out there. Over the years, I have developed a number of customized scanning methods to eliminate viruses and they take a long time to complete. There are no easy fixes.

Also remember that a computer that is possibly infected should not be on the Internet, and yes, email is the Internet. Pull the plug, if need be. The longer an infected computer is connected to the Internet, the worse things can become and the more likely you are to end up with damaged files or a computer that is not worth fixing.

The technique of sending out email while masquerading as someone else is called "spoofing." If you are the victim of spoofing, there's not much you can do. Sure, you can complain to the appropriate law enforcement authorities, but the likelihood of the bad guys being caught, charged, prosecuted and convicted is slim to none. If things get really bad, you may need to change your email address.

The best thing to do is to not get on the bad guys list in the first place. The bad guys sometimes use "bots" to scurry around then Internet, gathering email addresses. Don't allow your email address to become a clickable link on a website. Don't participate in email mass-forwarding schemes of jokes, stories and pictures, such as those emails you receive that are forwards of forwards of forwards, Fw: fw: fw:, etc., ad nauseum, where everyone is forwarding hundreds of different email addresses all around the Internet. Don't post your email address on public forums or message board websites. Whenever possible, avoid giving out your real email address.

These measures may seem harsh, but the Internet has a dark side that must be respected. Do so and you'll enjoy the happy Internet that you deserve.

Dave Moore has been fixing computers in Oklahoma since 1984. As founder of the Internet Safety Group, he also teaches Internet safety workshops for public and private organizations. He can be reached at 405-919-9901 or www.internetsafetygroup.com