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Are You Exposed? Part 1

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Can You be Scanned or Cracked?

Written on June 27, 2000 by Robert & Karen Vanderzweerde

Appeared in Greenmaster Magazine

It's a scary digital world we live in with viruses like ILOVEYOU, denial of service attacks on major web sites, junk e-mail (also known as 'spam'), questionable uses of private information, and computer crackers who break into systems. Crackers may steal information like credit card numbers, modify web sites, and cause other mischief.

Many people don't give out even a smidgen of information to anyone on the Internet, delete junk mail without opening it, run virus scans and backups regularly, disable browser cookies, and regularly change their well thought out passwords. They are confident that they are safe and secure.

Well, that may not necessarily be true. Every time you connect to the Internet, you are potentially exposing the entire contents of your computer for everyone on the web to scan, copy, or destroy. People with persistent or broadband connections (e.g. cable modems) are more vulnerable but those that use a dial-up connection are at risk too.

How can they do this?

Every time you connect to the Internet, you are assigned an IP address. This IP address allows you to communicate to other parts of the web (e.g. surfing to sites or downloading e-mail). You send out a request (e.g. type in a web site address) and your message goes to that server to fetch information. You IP address tells the server where to send the response. Without an IP address, no communication can occur.

The problem is that web traffic is two-way. Someone could send a request to your computer (e.g. copy all the files) and, unless you are protected, your computer will answer.

How is that possible?

There are several user-friendly features in Windows that make the computer easy for you to use without a lot of technical knowledge but inadvertently expose your computer.

For example, when you installed your modem and a connection to your Internet Service Provider (ISP), Windows "bound" that information into its network configuration. Since most people don't even know what binding is, Windows "binds" the information in the most promiscuous manner so that the feature you are likely to want is enabled (see Figure 1).

Figure 1 - Promiscuous Bindings

As you can see, the diagram doesn't make much sense unless you have a lot of computer knowledge. The flaw in being overly connected is that if you turn on "File and Print Sharing" on your computer, you will share your files directly to the Internet as well and anyone can copy them.

How can I protect my self?

The easiest thing to do is to turn off "File and Print Sharing". This can be found in the Network icon in the Control Panel. Double click on it to open it and then click on the "File and Print Sharing" button. The settings should look like Figure 2. If not, simply click on the checkmarks to remove them and then click on OK.

Figure 2 - File and Print Sharing

Note that password protecting your files is not sufficient if you have "File and Print Sharing" enabled and you are logged onto the Internet. I've seen password crackers decode passwords using common words, names, and places in two seconds. There is also another flaw in Windows where password attempts are unlimited and not logged (i.e. someone can try a million passwords on your computer and you won't even know it). It is better to disable "File and Print Sharing".

But they'll never find me.

Oh yes they will!

Internet hackers and crackers seem to have hours of time to hunt you down and get access to your information. In fact, there are automated scanning tools that try all IP addresses (yours included) and scan your ports for vulnerabilities. Someone could scan millions of IP addresses every hour without breaking a sweat.

With "File and Print Sharing" disabled, they can find you but will not be able to get in. To test yourself, there is a site that will scan your computer for free at and click on Shields Up! to get to the test programs. The message that indicates you are safe is "Unable to connect with NetBIOS to your computer".

If you are really concerned, there are products, known as firewalls, that you can install on your computer that will prevent access (even if you have "File and Print Sharing" enabled). Some of the more popular and proven products include:

  • Norton's Internet Security 2000
  • Black ICE Defender
  • McAfee's ConSeal Private Desktop
  • Zone Alarm (free too!)

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