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For most of us, the Internet is something of a mystery. We're not certain how it all works, and we don't know exactly how visible we are as we move around its virtual domain. Yet, we realize a certain percentage of persons understand Internet technology extremely well, and not all of them have the best intentions. That's enough to make the average user a little uncomfortable. After all, many of us are online all the time, exchanging information with friends and associates, doing research, reading the news. Naturally, we all wish we knew a little more about our day-to-day exposure. Who hasn't asked these questions: What aspects of my computer are visible to others? What parts can they access or manipulate? Are my emails and instant messages protected from prying eyes? Can anyone see what I'm doing while I'm on the Web? Of course, responses to these questions vary depending on your situation. But fortunately there are some general answers, and equipped with a little knowledge and protection, you can create a comfort zone for yourself on the Web.

The basics: ports and IP addresses

When you're connected to the Internet, others can see a few basic things about your computer. If they couldn't, there'd be no point in going online. The fact is, you need to make yourself known to make use of the Internet. Therefore, some level of exposure is inherent to online life. So, what exactly is visible? For starters, your ports and your IP address. Ports are information passageways between your computer and the Internet. Each port has a number and is dedicated to a particular function. For example, most Web traffic passes through port number 80. Emails travel through port 25. Ill-intentioned individuals can scan your ports to see which of your ports are open, and if some of the more interesting ones are available, they can use those ports to exploit your computer. Meanwhile, your IP address is a unique numerical identifier for your computer. It's kind of like your phone number or mail address, and without it, you wouldn't be able to receive anything over the Internet. It's also a handy way for hackers to keep track of your machine.

Despite the visibility of these basic details, it's possible to protect your computer from attack. Security solutions like Norton Internet Security shield your computer and its open ports from hackers. At the same time, they permit authorized traffic to pass through to your machine. If you don't have a firewall, you may want to at least avoid using a static IP address. With a static IP address, your computer has the same identifier each time you log onto the Internet. That makes you a sitting target. On the other hand, if your IP address changes every time you log on, you're a little more elusive. Check with your ISP to make sure your IP address is dynamically generated.

Windows file sharing exposure

If you're running a Windows operating system, other Internet users may be able to see your NetBIOS information. NetBIOS is a program used for basic network operations and communication, including file and printer sharing. If you're sharing files locally through NetBIOS and if you're also connected to the Internet, hackers may be able to view, download, or delete your files. The good news is, it's fairly easy to prevent attack by reconfiguring your NetBIOS settings.

Your surfing habits revealed

To some degree, other persons can see your movements on the Web. As you may know, your browser keeps track of your surfing history. It's a handy feature when you want to return to a site you recently visited. What you may not know is your browser also passes your most immediate history (i.e., the URL of the page you just left) to the ensuing Web site. Web site owners can use this information to study your surfing habits, especially if you return to their sites quite often. Fortunately, there's an easy way around this problem. Your browser cannot pass along the address of a referring page unless you click a link. So, if you don't want the owners of a Web site to know where you've just been, don't follow a link to that site. Instead, type the site's URL into your browser's address bar. It's also possible to reconfigure some browsers to block the transmission of referral addresses.

Spyware programs are even more invasive. They reside on your computer and gather information about your computing habits. They then send your profile over the Internet to the program's publisher. The publisher might use that information to target you through advertisements. Or, they might sell your profile to others. Most spyware ends up on your computer without your knowledge. However, if you're running Norton Internet Security, you'll be able to identify any program trying to access the Internet from your machine, including spyware. Once you identify and decide you don't want a piece of spyware on your computer, you can simply delete it and rest easy.

Emails and instant messaging

Unfortunately, your emails are not terribly secure. From the time they leave your computer to the time they reach their destination, many different persons—from mail server hackers to mail server administrators—can potentially read your mail. Likewise, your instant messages travel across the Internet unprotected. They're ripe targets for the curious to intercept and read. To mitigate potential privacy infringements, use a trusted mail service and make sure it employs powerful firewall protection on its mail servers. You should also frequently change your email and instant messaging passwords, especially if your using Web-based email like Yahoo or Hotmail. If your email contains highly confidential information, you may want to consider using key encryption technology. Although encryption requires a little effort, it's the best way to make certain only the intended recipients of your emails can read them. With regard to instant messaging, your own discretion is the best defense. If you have something important to say, save it for a more secure medium.

Viruses and other malicious programs

Certain malicious programs can make your entire system visible to hackers. For example, some Trojan horses place a remote control mechanism on your computer, providing full access to your machine. Once in control, a hacker can use your machine to attack others, or they can view, alter, or delete the contents of your computer. Malicious programs can make their way onto your system in a variety of ways—via email, Web sites, or even floppy disks. To protect yourself against that kind of exposure, install a trusted virus protection program like Norton AntiVirus.

Get an overall assessment

Although you could individually address each of these visibility issues, an overall security assessment is the best way to appraise the actual exposure level of your system. Symantec Security Check, a free assessment tool, evaluates most of your potential points of vulnerability, including your ports, your NetBIOS configuration, and your virus and Trojan horse susceptibility. Once Security Check has ascertained your exposure levels, it goes a step further and offers suggestions for protecting your system. After completing a full Security Check and taking the appropriate steps to secure your system, the mystery about your online visibility will disappear and you'll find the Internet a much more comfortable place to dwell.