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 Technology News | September 2007 
The World of Spam Filters - Blacklists and Whitelists
 easyCGI
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Not long after electronic mail arrived so did spammers - people sending unsolicited email to other computer users hoping to sell their goods or services. To combat the influx of unwanted bulk email some software companies offered spam filters to weed out real mail from 'junk email.'
In the beginning these programs worked well, but spammers soon learned to avoid such 'red flags' while using your settings to their advantage. This is why you see many spam messages titled 'order confirmation' or 're: your inquiry.' But there are two anti-spam techniques that have been gaining in popularity today. They're known as blacklists and whitelists.
Blacklists Spam Filters
Simply put, the anti-spam technique of blacklists is noting a list of traits that spam emails have. Such a list can be organized based on fields including who it comes from, the subject/body of the message or the originating IP addresses. When mail is banned from a particular IP address it's called 'source address blacklisting.' All mail from sources that have a known history of sending spam is blocked, regardless of who it comes from.
Taking things a step further is the act known as public blacklists. These public blacklists have no direct effect - they are simply published lists of addresses that have a bad reputation for spam. What makes this tactic special, and according to some people controversial, is how people use these address lists.
If a blacklist publishes the addresses of networks that do not meet positive standards of behavior, meaning some people in a network are using spam tactics, most network operators are forced with a choice. They will either conform to the standards or suffer reduced email connectivity of all their users. Essentially blacklists use the old tactic of peer pressure between email users and networks.
Basically, without blacklists many networks might welcome spammers as customers, but blacklisting motivates networks to keep spammers away.
Whitelists Spam Filters
Whitelists work under the assumption that everything you get is spam. However, that simplicity is one of its downfalls - everything is considered spam, even items you want. Whitelists eliminates all emails that are not pre-approved, which kills spam but it also abolishes any possibility of using email as a means of introduction.
For example, if you're a business you might stop the spammers, but you will also stop any customers from reaching you. While it's true that whitelists can have the option of verification, many customers might not want to go through the hassle and just avoid your business altogether. In addition, although it will block spam, whitelists also have an effect on order confirmations and mailing lists, which are often automatically generated, meaning you can't get those types of messages.
Rule-Based Filtering, Blacklists or Whitelists - What's the Answer?
It really comes down to determining your email needs and how you intend to use it. For example, if you have a business, then whitelisting might be too much trouble to your prospective clients and will equal lost sales. Then again, perhaps you only use the web for recreation and whitelisting isn't a huge issue. In the end only you can decide which method - rule-based filtering, blacklists or whitelists - work best for you. |
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