How do email spam filters work?
The simplest filters use keywords such as “sex,”, “xxx,” “viagra,” etc., in the subject line to attempt to identify and delete spam. These simple filters are easy to sidestep by spelling “sex” as “s-e-x.” There are, of course, many ways to spell “sex” if you are willing to add extra characters like that, and it is difficult for the simple filters to keep up. Also, simple filters are most likel to block “real” e-mail that you do want to receive. For example, if a friend sends you a recipe for curried chicken breasts, the filter blocks the e-mail because of the word “breasts.” More advanced filters try to take this simple approach quite a bit further and statistically identifies spam based on word patterns or word frequency. But there are still ways to get around them (mainly by using short messages). There are several organisations that publish lists of IP addresses that are used by spammers. Any large spammer will have an array of server machines churning out spam messages, and each se
