Spam continues to blight e-mail exactly 15 years after the term was first coined and almost 30 years since the first spam message was sent.
The term is thought to have been coined by Joel Furr, an administrator on the net discussion system Usenet, to refer to unsolicited bulk messages.
More than 90% of all e-mail is spam, according to anti-spam body Spamhaus.
"Spam is a real life arms race," said Mark Sunner, chief analyst at online security firm Message Labs.
Billions of spam e-mails are sent each day, blocking mail servers, slowing down networks, infecting people's computers with viruses, helping hijack machines and generally making the internet a painful experience for many.