What is a Spam?

As wikipedia says, Spam is the abuse of electronic message system to indiscriminately send unsolicited bulk messages. While the most widely recognized form of spam is e-mail spam, the term is applied to similar abuses in other media: instant messaging spam, Usenet newsgroup spam, Web search engine spam, spam in blogs, wiki spam, Online classified ads spam, mobile phone messaging spam, Internet forum spam and junk fax transmissions.

In other words, we can say spam is flooding the internet with multiple copies of the same message, in an attempt to force the message on people who would not otherwise choose to receive it. Almost all spams are commercial advertising, often for dubious/malicious products, get-rich-quick schemes, etc. Spams cost the sender very little to send, most of the costs are paid by the recipient or the carriers rather than by the sender.

E-mail spams target individual users with direct mail messages. E-mail spam lists are often created by scanning Usenet postings, stealing Internet mailing lists, or searching the Web for addresses. Email spams typically cost users money out-of-pocket to receive. Many people - anyone with measured phone service - read or receive their mail while the meter is running, so to speak. Spam costs them additional money. On top of that, it costs money for ISPs and online services to transmit spam, and these costs are transmitted directly to subscribers.

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