Spam (e-mail)

Spam is any unwanted email message, usually an advertisement, broadcast to a great number of users. Although it is used almost exclusively in reference to email, the term originated in Usenet groups. Usenet hosted (and still hosts) a great number of topics or 'groups' to which a user can subscribe. When the same message was 'crossposted' - that is, copied - to a great number of groups, the messsage was said to be 'spam'.

Using the word 'spam' in this way is a reference to a Monty Python sketch. In the sketch, people are gathered in a restaurant (including, inexplicably, a group of Vikings in full 12th-century regalia) and pointlessly repeat the word 'spam' over and over. The use of the term in Usenet alluded to this absurd and annoying duplication. Some, but not all, of the early Usenet 'spammers' or cross-posters were in fact unscrupulous advertisers, who had discovered a free advertising channel by ignoring Usenet's Terms of Service.

As email became more available and popular, advertisers misused it in a manner similar to Usenet, and the 'spam' term was applied to this more ubiquitous and serious problem.

Spam is illegal to broadcast in the US and many other countries. Spam has sparked something of a technology arms race between those who seek to illegally profit from sending spam, and those trying to eliminate it. Spammers harvest, trade and sell collections of email addresses; spam-fighters working at various stages of the internet infrastructure erect spam-filters to detect and eliminate spam. Spammers attempt to defeat those filters by disguising their emails as legitimate by various means, for example, including random bits of text to make each email different.

The term 'spam' is sometimes more loosely used to describe any act of for-profit promotion in a public forum.