Windows XP / Networking

SMTP and spam

The ability to spoof a return address and easily mail the same message to multiple recipients has lead to the uncontrolled outbreak of junk email, or spam. Spam, by some accounts, represents up to 50% of email traffic and is popular for one reason: email is dirt cheap. Junk physical mail is annoying, but it has a certain cost of delivery, and each piece must be handled and addressed, even if the name used is "occupant." This inherent cost limits the total amount of junk mail sent out because someone has to pay the bill. Email, on the other hand, has few costs: scraping up a few million email addresses off newsgroups and chain letters is not really that hard, especially if software is used to scan newsgroups and other places where addresses are densely displayed. Plus, launching and sending such messages is largely automatic; just turn on the spambot machine, and forget it.

Some email recipients resent the intrusion, and send responses asking that they no longer be disturbed. This proves the user's email is valid and increases the value of the address when compiled into lists sold to other spammers. Other addresses are nonexistent or already abandoned. Email systems will send back notices to the sender to this effect. As the bad addresses bounce back and fill up the sender's inbox, there are no worries: it probably was not a valid inbox. Most spammers are careful to avoid using their real Internet addresses.

Tracking spammers down requires a lot of detective work; for example, you have to request that ISPs and the owners of various intermediate systems check their logs. This makes detection difficult. Because most spam today leads respondents to a web page anyway, dead-letter information is not really important to the sender. In fact, as stated, the most malicious spammers mimic a return address of someone they wish to annoy, letting them deal with the crush of dead-letter notifications, which often come in such volume as to shut down the unlucky victims email account in order to protect the server.

The cost-per-thousand of spam is so low that any spammer with technical savvy and a little software can send millions of junk emails a day from a very humble facility. The potential returns make it worthwhile grubbing about for addresses.

Recent rule changes have made it illegal to send spam. However, just because a law is in effect in one country does not mean it is valid in others. Many spammers operate remotely, from countries that don't get too negative about earning revenue from a nonpolluting, high-tech industry such as bulk email. Other spammers use hacking techniques to turn ordinary computers, perhaps yours, into machines that will either generate or relay their spam for them. The best way to cope is likely the same way you cope with unsolicited physical mail. Use the antispam features of your email client software to filter undesired email into the recycle bin before you even see it.

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