Spam sent to UK internet users has nearly quadrupled since the beginning of the year, and most of it was sent from within the UK.

According to Clearmymail, which develops spam filtering software, the UK is first in the list of the top 10 countries sending spam to UK email accounts.

However, these are not home-grown spammers; they are from the US, Russia and China.

The spammers are hijacking PCs and web servers in the UK used to host websites, and then using these as mail servers to send out spam.

Dan Field, Clearmymail’s managing director, said this was a worrying trend.

“The spammers are launching more sophisticated and cleverly targeted attacks. To make these attacks more ‘local’ they are finding vulnerabilities in websites, using these to infiltrate the hosting servers and sending spam through these," he said.

"There is also the problem of botnets; we have seen a huge upturn in the last three months. People are still not updating their security regularly, so malicious software in spam can infect their PCs.

"But another problem for computer users is many attacks are going under the radar. They are not mass attacks and this means security software programs may not have developed the protection until it is too late for some people."

The report showed that on average 30,846 spam emails were blocked per customer in the second quarter of 2008, compared to just 8,156 emails blocked per customer in the first quarter of the same year. The company said the number of spam emails it had blocked increased to approximately 22,690 spam emails in just three months.

These emails show that phishing attacks are increasing, with the Royal Bank of Scotland appearing to be the main company targeted by phishing attacks. Orange customers received the highest percentage of spam of any internet serv ice provider the company surveyed.

Although the UK is now the number one culprit, the USA is still highly ranked at number two. UK internet users are also getting more spam from European countries.

“These statistics are becoming increasingly worrying and for the average amount of spam blocked per person to have nearly quadrupled in the last three months suggests that action desperately needs to be taken,” said Mr Field.