Spam email is a form of commercial advertising which is economically viable because email is a very cost-effective medium for the sender. If just a fraction of the recipients of a spam message purchase the advertised product, the spammers are making money and the spam problem is perpetuated.
Spammers harvest recipient addresses from publicly accessible sources, use programs to collect addresses on the web, and simply use dictionaries to make automated guesses at common usernames at a given domain.
Spammers often conceal or forge the origin of their messages to circumvent laws, service provider regulations, and anti-spammer lists used by anti-spam software.
At present more than 95% of email messages sent worldwide is believed to be spam, making spam fighting tools increasingly important to all users of email.
Why is spam a problem?
In addition to wasting people's time with unwanted email, spam also eats up a lot of network bandwidth. Consequently, there are many organisations, as well as individuals, who have taken it upon themselves to fight spam with a variety of techniques. But because the Internet is public, there is really little that can be done to prevent spam.
