Spammers are increasingly targeting social networking websites like Facebook and Twitter, computer experts warned today.
Growing numbers of cyber-criminals try to trick users into revealing passwords so they can hijack their personal profiles and send out messages promoting everything from pornography to medication.
New figures from IT security firm Sophos also reveal that the UK is now the world's 10th worst offender for relaying spam.
Some 2.7% of all junk e-mails came from compromised computers in Britain in the last three months of 2008 - up from 2.5% in the same period a year earlier.
The US retains its crown as global spam king, being responsible for relaying 19.8% of unwanted e-mails between October and December last year.
In January 2004 Microsoft co-founder Bill Gates predicted spam would be "a thing of the past" within two years.
But five years on it remains a serious problem - and is increasingly likely to be designed to infect users' computers to steal sensitive information such as banking details.
Graham Cluley, senior technology consultant at Sophos, said around 27 out of every 28 e-mails sent are now spam.
He called on the Government to fund a major advertising campaign to raise awareness of the problem among ordinary computer users.
"More people are getting connected, and they're not geeks any more," he said.
"Now it's your mother-in-law who's online and who's on Facebook - and maybe giving away too much information."
Cyber-criminals have realised that Facebook users can be more easily fooled into clicking on a link if it appears to come from one of their friends.
Mr Cluley said Britain "could do better" on spam, and advised people to make sure their anti-virus software, firewall and Windows security patches were up-to-date.
He added: "The rumours of spam's death have been greatly exaggerated over the years.
"The threat remains alive and kicking despite increased legal action against spammers, the occasional takedown of internet companies which assist the cyber-criminals, and constantly improving anti-spam software.
"Many IT professionals cast doubt on Bill Gates's assertion back in 2004, deeming the timeframe of his pledge to be unrealistic.
"Although the latest stats show that the proportion of spam relayed per country may have decreased year-on-year, spammers have turned to more creative - not to mention devious - methods to ensure their messages reach as many unsuspecting computer users as possible."