Can They Really Stop Spam?

2007-03-08 10:33:40

( Computers )



The growth of spam has been so widespread that you see it every time you check your mail. And like other people, you are probably fed up seeing spam occupy most of your inbox space. To solve your problem, many anti spam solutions have been proposed and implemented. These fall into four categories: filters, reverse lookups, challenges, and cryptography. While these options may be feasible for some, you may find them limited in terms of their ability to stop spam.

You might be familiar with the spam filtering service. Word Lists check the body of your incoming e-mail for common words usually associated with spam. Black Lists check the IP Address of the sender against known spam addresses, while any site listed in the White List is considered safe. Summaries of spam mail are stored in Hash Tables which are used for comparison with your incoming e-mail. Although filters organize and separate your mail into spam and non-spam, it does not stop spam from reaching your inbox in the first place.

Most spammers use forged sender addresses for many reasons: to avoid prosecution; to hide their identity from angry recipients of spam mail like yourself; and to reduce the chances of their network access being cancelled by their Internet Service Provider. The Reverse Lookup approach seeks to verify whether the e-mail address listed in the “From:” header in your mail has been forged to make it look like it came from a valid domain. If you are a user that frequently change IP addresses, like mobile and dial-up users, you will be blocked by reverse-lookup systems.

Challenges attempt to discourage bulk-senders by slowing the bulk-mailing process. There are two types: Challenge-Response (CR) systems and Computational Challenge (CC) systems. A CR system provides a new sender a challenge that they must comply with before their email is allowed to be delivered to your inbox, and their address added to the list of permitted senders. A spammer who uses fake e-mails will not receive the challenge, while those who use legitimate e-mails won’t have the time to respond to all challenges. CC systems will add a “cost” to sending e-mail, usually by delaying the delivery of e-mail by a certain amount of time. Bulk mailers are usually not discouraged by this tactic, which affects slower systems more than faster ones. Mailing lists become impractical, since they are also affected by this system.

Cryptography is also used to stop spam from invalid addresses. Without a proper certificate, a forged e-mail is easily identified. Its fault lies in its inability to be properly implemented on a global scale. An automated system that generates certificates to you, other users, mail servers or mail clients will be subject to abuse from spammers who could use this system to send out “authenticated” spam.

While some of these prove effective in contained environments, spammers constantly adapt. Unless anti spam solutions do the same, they won’t prove to be as effective tomorrow as they did today.


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