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Home Network Vulnerabilities: Spam, Cookies, Pop-Ups, Spyware, and Scams

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Jul 1, 2005.

Chapter Description

In addition to viruses and worms, there are some other annoying programs and files out there that you need to protect your home network from. This chapter focuses on spam, cookies, spyware, and scams—what they are, how they work, and how to get rid of or at least control them.

From the Book

Home Networking Simplified

Home Networking Simplified


In addition to viruses and worms, there are some other annoying programs and files out there that you need to protect your home network from. This chapter focuses on spam, cookies, spyware, and scams—what they are, how they work, and how to get rid of or at least control them. For the most part, these types of files are not as dangerous as the others we discussed in Chapter 15, "Viruses and Other Malicious Software"—none of them will remove or destroy data for example—but they are still common, extremely annoying, and in some cases, they can do things without you knowing about it.


Spam is the common name for unsolicited e-mail and it is a problem that is rampant on the Internet today. Because of spam, a whole sub-industry of spam blockers has cropped up and is a major concern of Internet service providers (ISPs). Major service providers claim that they block on the order of 2 billion (yes, billion) unsolicited e-mails everyday and have put the effort to stop spam at the top of their priority lists. One of the reasons that spam is so widespread is that it is extremely easy to send out millions of e-mails with little cost.

How Spam Works

Spammers do their dirty work by purchasing or creating giant e-mail lists and automated mailing tools called spambots. The lists are usually compiled from web pages where people provide their e-mail address as part of a registration process. Usually, there is a box that is checked "yes" by default saying something along the lines of "Yes, please share my e-mail with your sponsors for related offers." If you agree, by leaving the box checked, you have just given the site permission to sell and resell your e-mail address to spammers. Although most spam gets caught by filters or deleted by the recipient, some of it is answered and that is why the spammers keep at it. It is really a matter of odds. Even if the response rate is 0.5%, it cost next to nothing to send spam to upward of 10 million e-mail addresses. At that rate, the spammer just pulled in 50,000 new customers.


Spam is unsolicited commercial e-mail, and it is a huge problem. Some large ISPs claim that they block over one billion e-mails a day and some still gets through. Here is one example of how spammers get their info.

  1. Larry registers on a web page and leaves the "I want to know more box checked.
  2. The web page's owner creates a giant list of e-mail addresses, which is sold to multiple spammers.
  3. A spammer collects millions of e-mail addresses from multiple sources and starts sending e-mails.
  4. Despite your ISP's efforts to block spam, it still comes through in droves. Be careful with whom you share your address

How to Block Spam

There is a good chance that your ISP has some sort of spam-blocking feature available and, if spam is a problem for you, we suggest starting there. Your ISP probably uses some basic filters such as looking for keywords or multiple (100,000+) instances of an e-mail from the same source IP address. Unfortunately, spammers (those who create and send spam) are pretty good at staying ahead of the ISPs by using random or misspelled words or by constantly changing IP addresses as they send e-mails. (There is also talk of anti-spam legislation, but spammers can easily set up shop in countries with looser laws.) If the ISP filters are not blocking enough spam, you can purchase or download software that will provide a second layer of protection on your system. Typically, these programs use advanced algorithms to recognize and block spam but they are not perfect because sometimes spam gets through the filter, and sometimes legitimate e-mail gets blocked (essentially a false positive). You can modify the options in this program so that the blocking rules are customized. Be sure to check the folder that the spam blocker drops trash e-mail into every once in a while to make sure you don't miss "real" e-mail.

We recommend that in addition to using the ISP and commercial blockers that you set up a dirty e-mail address. What we mean by dirty e-mail address is an e-mail address that is only used for the purpose of registering on web pages. Given that most ISPs will allow several e-mail aliases with a standard account, you can reserve one for this purpose and still have plenty for the legitimate users in the home.

After you do this, only give your "real" e-mail out to people you know and use the dirty one for everything else. If you find that you do want some of the e-mail that comes into the dirty account, you can notify the sender to use your real e-mail address. Keep in mind that most legitimate commercial sites will not resell or share your e-mail address without your permission, but it's up to you to make sure that you read the fine print and uncheck any boxes that were pre-populated. This is always a red flag.

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