This week, the world marks an anniversary that has changed the face — and other anatomical regions — of e-mail inboxes everywhere: the first known spam e-mail was sent 30 years ago on Saturday.

But the message, sent on 3 May 1978 by a marketer for the now defunct DEC computer company, went to around 400 people on the west coast of the United States and it wasn't called spam. Also, the sender dispatched it without any ill intent.

Spam got its name from a skit by the television show Monty Python's Flying Circus, in which a group of Vikings in a restaurant that serves all of its food with Spam tinned meat sing a song repeating the word ad nauseum, says Brad Templeton, who has thoroughly researched the subject.

"Thus, the meaning of the term at least: something that keeps repeating and repeating to great annoyance," Templeton, who was dabbling in the internet in the 1970s — when it was still the US government-run Arpanet — says on his Web site.

Spam was never supposed to live this long.

Speaking at the World Economic Forum in Davos, Switzerland in 2004, Microsoft chairman Bill Gates famously said he had a solution that would defeat spam by 2006.

In 2008, the percentage of spam sent to account holders on Gmail — the e-mail service offered by Google — quadrupled between 2004 and 2008, climbing from 20 percent to around 80 percent.

"To give you some sense of scale, we have tens of millions of users worldwide," Gmail's Jason Freidenfelds said.

Spam methodology has also changed in the past 30 years.

Whereas the sender of the first spam had to type in each recipient's address individually, today the job is often done remotely using cyber-monsters called botnets.

Botnets have hijacked around 30 percent of personal and office computers with inadequate security features and use them to dispatch millions of unsolicited e-mails each day, Templeton said.

Spam content and motives have evolved since the initial 1978 e-mail, which was an invitation to a product launch.

Spam today comes from Nigerian "princes" or fictitious relatives of deceased African dictators intent on hoodwinking e-mail account holders into parting with bank details or cash, in exchange for a slice of the wealth stashed in an offshore account.

The most common form of spam remains the e-mail that tries to sell you a replica Rolex, a miracle weight loss formula, or medication to enlarge anatomical parts or enhance sexual prowess.

Twelve percent of internet users have bought something offered to them by spam, according to Graham Cluley, senior technology consultant at IT security company Sophos.

"Maybe these people are too embarrassed to go to their doctor or they want to save some money but we have to educate them to report spam, delete spam, but absolutely never buy off spam," he said.

"A Brazilian model died after using weight loss pills she bought off spam ... [spammers] do not have a strong ethical sense," he warned.

Last year, Americans were tricked out of US$239.09 million (AU$253.62 million) by Internet fraudsters. 75 percent of the victims had responded to an unsolicited e-mail, according to a report by the FBI.

ZDNet.com.au's Jo Best contributed to this report.