In 1978 the first spam e-mail--a plug from a marketing representative at Digital Equipment Corporation for the new Decsystem-20 computer--was dispatched to about 400 people on the Arpanet. Today junk correspondence in the form of unwanted commercial solicitations constitutes more than two thirds of all e-mail transmitted over the Internet, accounting for billions of messages every day. For a third of all e-mail users, about 80 percent of the messages received are spam. Recently spam has become more threatening with the proliferation of so-called phishing attacks--fake e-mails that look like they are from people or institutions you trust but that are actually sent by crooks to steal your credit-card numbers or other personal information. Phishing attacks cost approximately $1.2 billion a year, according to a 2004 Gartner Research study.
The phenomenon of spam afflicts more than just e-mail. Inside chat rooms lurk "robots" that pretend to be human and attempt to convince people to click on links that lead to pornographic Web sites. Instant messaging (IM) users suffer from so-called spIM--e-mail spam cognates. Blogs can be corrupted by "link spammers" who degrade Internet search engine operations by adding misleading links to sites that distort the utility ratings of Web sites and links.