How Spam E-mail Works

            Spam is unsolicited e-mail that is sent to you, usually by commercial firms that want to sell you goods or services. The name spam comes from a Monty Python skit where a person ordering food from a restaurant finds that all of the dishes come with spam. Spam is sent as bulk mail, often to 10 000 or more people at once. Spam is inexpensive so its use is now very common. Paper junk mail costs money because the mailer has to pay for paper, envelopes, printing, postage, and the cost of buying addresses. However, e-mail spam is virtually free, so its use has taken off.

            The first thing a spammer needs is a list of e-mail addresses. A list can be bought off a company that compiles them. These companies get the e-mail addresses by using automated software robots. A possible source for the robots to get the addresses from is Usenet newsgroups. The robot will go into every message posted, and take the e-mail address of the person who posted each one. Robots can also go into e-mail directories and chart areas to harvest addresses.

            The spammers use the list, along with mailing software, and send a spam message to every person on the list. The message may include a Web site, etc. for the recipient to get information about whatever is being sold. Some spammers include a return address in the e-mail for people who want to be removed from the mailing list. However, this is not very common because most people would choose not to receive these e-mails.

            Spam offends many people, so spammers try very hard to hide their true e-mail addresses. One way they can do this is by forging the From, Sender, and Reply fields, so that it seems like someone else has sent the message. This is sometimes called “spamouflage.” To hide their addresses even better, spammers can relay their bulk spam to a server that is not associated with them. Then that server will send the mail out. Sometimes spammers will relay their bulk mail through several different servers to make tracking the original sender extremely difficult.

How Spam is Blocked

            Spam can be blocked in many ways:

• The first, and least useful way, is to write back to the spammer’s removal address. Spammers try very hard to hide their true addresses, so this doesn’t usually work. The e-mail address they list is often a dead address.
• Some e-mail software lets you block messages from certain e-mail addresses. This is called a “spam filter.” When you put an address in your spam filter, you will never receive mail from that address again. However, this will not always work because spammers often change their addresses and forge the fields in the e-mail headers.
• Internet service providers can block messages from getting into their network. A router examines all incoming mail to the ISP. The router is told to block mail coming from certain addresses from getting into the network. These addresses are put in a routing table, and can be changed at any time to add new spammers. Routing tables do not always work since spammers often change their addresses.

Since it is virtually impossible to block all spam, the best way to avoid it is to protect your e-mail address like you would protect an unlisted phone number. Only give your e-mail address to people you really want to have it, and don’t let them give it away. Also, don’t type your address into any forms on Web pages, or when software programs ask you to register because that is how you end up on mailing lists.

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