Spam Filtering

Mon Sep 1 12:01:06 GMT 2003 Spam Filtering

There's been a thread on some Linux newsgroups lately where a person named Alan Connor has been vehemently attacking SpamAssassin and slashing out viciously at anyone who points out the errors in his posts. I've stuck an interesting reply to one of them here: Best of the Newsgroups: Spamassassin vs. whitelists.

Mr. Connor has a "whitelist" script which he thinks is superior to SpamAssassin. Whitelisting means that you maintain a list of people you will allow to send you mail. You seed that list from your address book originally, and people who aren't on that list get challenged and need to prove they are a real human being before their email will be let through.

For individual home users such a scheme can make sense. It doesn't work so well for businesses though: I don't want to annoy potential clients with this sort of extra work. But what's really amazing is that Mr. Connor totally misses a very important point: a lot of the most annoying email we get nowadays has forged addresses, and is often from people who have already sent us legitimate mail. While the whitelist would let these go through, Spamassassin can be helpful in eliminating them, and there's no reason at all that you can't run BOTH SA and a whitelist.

In fact, that's true for many spam solutions: very few of them conflict, and in fact their additive effect can be useful. I reject mail from certain domains right at my server, do some subject filtering in my pop script (yes, that means if you send me email about a "wicked screensaver" I may not get it), run it through SpamAssassin after that, and then let Apple's Mail.app Bayesian filters have a crack at it. The final check is Mail.app's own filters, so by the time your email reaches me it has gone through five filter steps, and I'll be adding a sixth at the server soon.

It's sad that we need to go to all this trouble to make email usable, but otherwise I'd get 2,000 or more junk emails every day. Some folks have ideas to improve that: http://www.ietf.org/internet-drafts/draft-weinman-amtp-00.txt suggests authenticated SMTP using digital certificates to verify the source. One problem is that digital certificates cost money, though it might be that if a lot of us started buying them, prices would come down. The biggest flaw there is making a switch-over: I can't cut off people NOT using an authenticated mail scheme until everyone is doing it.

Macworld Mac Security Superguide $9.99

Jump to Comments

Many of the products and books I review are things I purchased for my own use. Some were given to me specifically for the purpose of reviewing them. I resell or can earn commissions from the sale of some of these items. Links within these pages may be affiliate links that pay me for referring you to them. That's mostly insignificant amounts of money; whenever it is not I have made my relationship plain. I also may own stock in companies mentioned here. If you have any question, please do feel free to contact me.

Specific links that take you to pages that allow you to purchase the item I reviewed are very likely to pay me a commission. Many of the books I review were given to me by the publishers specifically for the purpose of writing a review. These gifts and referral fees do not affect my opinions; I often give bad reviews anyway.

We use Google third-party advertising companies to serve ads when you visit our website. These companies may use information (not including your name, address, email address, or telephone number) about your visits to this and other websites in order to provide advertisements about goods and services of interest to you. If you would like more information about this practice and to know your choices about not having this information used by these companies, click here.