The UK leads the world in home computers that have been hijacked by malicious hackers, warns a report.
Research by security firm Symantec shows that 25% of the world's remotely controlled PCs are found in Britain.
The compromised computers are being used to send spam, launch attacks on Websites and steal identities.
Symantec said the rise of broadband in Britain and user ignorance about the dangers of the net contributed to the figure.
It found that 25.2% of all the zombie machines detected were in the UK compared to 24.6% in the US and 7.8% in China.
Despite this the US still leads the world in the number of attacks launched by machines on its soil.
The good news about the zombie networks is that fewer seem to be in use on a daily basis.
Symantec found that the average number in use declined from 30,000 per day in July 2004 to about 5,000 in December,
However, the compromised computers are being used for progressively criminal ends to mount attacks on websites for extortion or in an attempt to steal confidential information.
Nigel Beighton, director of enterprise strategy at Symantec Europe, said the rise of zombies in the UK was due to the 93% increase in broadband connections in the UK over the last year.
"Unfortunately, new broadband customers may not be fully aware of the additional safety precautions that need to be taken when using an always-on high-speed internet connection," he said.
"Education still remains the number one challenge," he added.
The threat report also found that two programs that create zombies computers were in the top 10 malicious programs for the last six months.
The numbers of variants of one zombie creator, called Spybot, has grown to 4,300 in the last six months.
Many people have been tricked into opening an email attachment bearing a virus which has resulted in their PC being hijacked. Others have simply been found by worms that scour the Web for machines suffering one of many widely known vulnerabilities in Windows software.
Also growing fast are threats from phishing, spam, spyware and adware.
More than 33 million phishing attempts a week have been stopped by anti-fraud filters created by Symantec subsidiary Brightmail.
Spam totals were up 77% on the last six months with Symantec/Brightmail now stopping more than 1.2 billion junk mail messages a week.
Many PCs were contracting spyware and adware programs from Websites set up to snare victims. But, Symantec noted, much spyware was bundled in with other programs.
Symantec predicted that future security threats will include more viruses for mobile devices and attempts to conceal malicious in media clips.
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