Consider just how much we do online. We exchange emails and share photos with people. We chat with friends, and play online games, read news stories, and download the latest music. And we do it all from the comfort of our kitchen tables, bedrooms, and favorite cafes. Unfortunately, the things we store on our computers are at risk when we're online, as are our identities and private information. Hazardous viruses, Trojan horses, worms, and other threats lurk behind some of the Web sites we visit and spread over two of our most popular communication tools—email and IM. However, with knowledge and the right tools, you can get a handle on these threats and keep you and your possessions safe.

When you're surfing

As you cruise the Web, there are myriad ways to contract damaging viruses. In a common scenario, virus writers will exploit vulnerabilities in your browser, downloading malicious code in the background when you open a page. Others use nasty little program scripts to infect your computer when you visit a page and activate the embedded program. And sometimes a virus or a piece of spyware is hidden behind an intriguing or misleading image or text link. In each of these cases you merely have to visit a site or click a link to become a victim.

However, because many of these methods are well known, there are things you can do to protect yourself. For example, you can turn off your browser's scripting, Java, and ActiveX capabilities. If you need them to make something work on a site you trust, just turn them back on. And because a lot of malicious code is designed to exploit known security holes, you can install browser and operating system security patches as soon as they become available. For the same reason, you may want to try alternative browsers or operating systems. All of these things can reduce the likelihood your computer will get infected as you surf the Web. However, the most important thing you can do is install a high quality antivirus software one that automatically blocks known viruses, Trojan horses, worms, and other malicious code. And because new viruses appear all the time, you need to be disciplined about updating your antivirus software regularly. You may even want to buy an antivirus tool that can update itself automatically.

When you're using email

Just as your basic Web site can pose a threat, so can something as simple as opening an email attachment. In fact, virus writers love to send mass emails enticing recipients to activate a virus they've planted in an attached file. These emails are often easy to spot because they're sent by someone you don't know. However, they sometimes appear to come from a friend—most likely because your friend's computer has been infected by a self-propagating virus or worm. And attachments aren't the only way to contract viruses through email. Email messages containing HTML can also be a hazard. Just like a Web page, they can download malicious scripts through security holes or embedded scripts.

So, the first rule of email is to be careful with attachments. Open them only if you know who sent them and what's inside the file. If you get a random email attachment, verify its authenticity before opening it—even if it's from a friend. If you can't verify it, delete the whole email. To avoid contracting a virus through HTML email, turn off your email program's HTML and scripting features. And because many viruses are spread via spam email, get a good email filter to minimize the amount of spam in your inbox. Finally, and most importantly, make sure your antivirus solution automatically scans email attachments.

When you're on IM

IM file attachments, like email attachments, can carry destructive viruses, worms, and Trojan horses. In fact, there's a new breed of mass-mailing worms that uses IM buddy lists to distribute themselves. And because it's so easy to create an IM identity and make contact with people, instant messaging is a ripe medium for online scams, identity theft, and other predatory behavior. This is a particular danger for children, who may be approached by online strangers with criminal intent.

So, don't open an IM attachment unless you've verified what's in it and who it came from. To protect your privacy and identity, use a solid account password and change it often. And make sure your family's IM profiles don't contain personal information—especially phone numbers, addresses, photos, or anything that could connect you or your children with your IM identities. Finally, just as certain antivirus programs scan email attachments, some can also automatically scan IM attachments. Make sure yours does.

The online landscape is ever-changing, with new and better technologies emerging overnight. On the downside, viruses and other threats appear just as quickly and often. So, stay vigilant, stay informed, and use the best tools you can find to keep these threats at bay.