Security firm Sophos has launched a Spam Pledge to mark the 30th anniversary of junk email, urging users to help stamp out the scourge of spam.

The first known instance of unsolicited commercial email was sent on 1 May 1978 by Gary Thuerk, a marketing rep at Digital Equipment Corporation, to 393 users of Arpanet, the precursor to the internet.

The problem has since escalated to epic proportions. Estimates of how much of today's email is spam varies between 80 and 95 per cent, and Sophos Labs discovers a new spam-related webpage every three seconds.

"Gary Thuerk could never have imagined what he was starting when he sent that mass email 30 years ago," said Graham Cluley, senior technology consultant at Sophos.

"There is a generation of people today who have never worked in a world without spam clogging up their inboxes.

"What's worse is that a lot of spam is deliberately malicious, aiming to steal bank account information or install malware. People who buy goods via spam are merely perpetuating the problem for all users and must be stopped."

The driving factor behind the Spam Pledge is an appeal to internet users to resist responding to spam adverts or clinking on the links.

A recent Sophos survey revealed that 11 per cent of respondents admitted to having bought goods via spam.

"The internet community needs to do what it can to make sure that spam doesn't celebrate a 40th or 50th birthday," said Cluley.

"That means educating the public about never buying goods sold via spam. If you receive an unsolicited email message advertising goods, don't buy, don't try, don't reply."

To help drive its pledge, Sophos has created a Facebook group entitled 'The Sophos Spam Pledge, and a YouTube video of people taking the oath and promising never to click on links in unsolicited email.