E-mail spam

E-mail spam, also known as unsolicited bulk email (UBE) or unsolicited commercial email (UCE), is the practice of sending unwanted e-mail messages, frequently with commercial content, in large quantities to an indiscriminate set of recipients.

Spam in e-mail started to become a problem when the Internet was opened up to the general public in the mid-1990s. It grew exponentially over the following years, and today comprises some 80 to 85% of all the email in the world, by conservative estimate; some sources go as high as 95%.

Pressure to make e-mail spam illegal has been successful in some jurisdictions, but less so in others. Spammers take advantage of this fact, and frequently outsource parts of their operations to countries where spamming will not get them into legal trouble.

Increasingly, e-mail spam today is sent via "zombie networks", networks of virus- or worm-infected personal computers in homes and offices around the globe; many modern worms install a backdoor which allows the spammer access to the computer. At the same time, it is becoming clear that malware authors, spammers, and phishers are learning from each other, and possibly forming various kinds of partnerships.

E-mail is an extremely cheap mass medium, and professional spammers have automated their processes to a high extent. Thus, spamming can be very profitable even at what would otherwise be considered extremely low response rates.

An industry of e-mail address harvesting is dedicated to collecting email addresses and selling compiled databases. Millions of email addresses can be cheaply purchased.

An e-mail program detecting spam messages. Spammers frequently disguise their messages with obfuscated text.

From: Wikipedia