News flash: Spammers and virus writers don't just stick to e-mail these days; they plan to invade your IM, too. Even if you haven't yet received chat-borne viruses or unsolicited instant messages, it's only a matter of time.

According to the Gartner Group, more than 50 percent of Americans use an instant messenger at the office. With such a populated hunting ground, it's not surprising that spammers are licking their chops. Invite some virus writers to the party, and you'll have scary security issues on your hands. Virus writers have already shown us that they know a thing or two about exploiting messengers. Although a lot of antivirus programs can detect viruses lurking in your e-mail, none is adept at monitoring your IM.

Indeed, instant messaging is a security disaster waiting to happen, so you should take precautions to make sure your chat app is as safe and secure as possible and to control pesky--and often pornographic--IM spam while you're at it. Whether you use just one or several IMs or a multiservice chat app, such as Trillian, you'll probably want to tweak your security and privacy preferences to make sure the chat app you use plays by your rules, not some spammer's. Each IM has its own particular maze of cascading menus and ambiguous options. We break them down for you.

Block IM invaders
Decrease your odds of contracting a virus or attracting a spammer by following these general guidelines for safe messaging.

How to configure your IM
Each IM fends off troublemakers in its own way. We'll show you how they work.