He probably meant well and he obviously loves his family but the programmer who unleashed the latest computer virus was not a popular man in Sussex yesterday.

East Sussex County Council had to shut off computers at Pelham House, Lewes, after being infected by the Nachi worm, which emerged this week.

The virus is thought to have been created to try to counter the MSBlast virus, which first appeared in July and is estimated to have infected more than 500,000 machines.

MSBlast exploited a month-old security loophole to infect internet-connected Windows PCs, forcing computers to constantly reboot every 60 seconds.

The Nachi worm, also known as Welchia, infects computers and searches for traces of the Blaster worm to remove but can cause complications of its own, such as clogging and slowing machines.

Contained inside the worm is the text: "I love my wife and baby :)"

Marc Liron, IT manager of the charity Clarion Projects at the Whitehawk Inn Training Centre, said: "People have been calling it the Dirty Harry virus. Someone obviously wanted to try to clean things up.

"But no virus is a good virus. It's still an invasion of your machine and could cause problems. You should have control of your machine, not have some third party interfering."

Council staff first realised they were the victims of the bug on Wednesday morning.

Nick Deyes, the council's head of IT, said: "We had to drop everything and work round the clock to get the network fixed. We have prioritised those areas where the public may be affected."

Hand-written media releases had to be composed on the council's headed notepaper.

Rosy Kempston, who took over this week as the council's head of media, said: "I hope this isn't a bad omen for me. Everyone has been rushing about trying to fix things.

"It's been a bit of a pain for us, though the effect on the public is minimal. It could have been worse if the schools weren't on holiday. We've had difficulty collating the GCSE results but that hasn't affected the kids getting the results."

People due to use People's Network terminals at the county's libraries were being advised to phone in advance to check whether the PCs were working yet.

Other organisations have also suffered from Nachi, which clogged the ticketing systems of Air Canada and the corporate networks at Lockheed Martin.

Mr Liron has been counselling many distressed virus victims through his web site devoted to Windows XP, at www.updatexp.com The site, which receives 4,000 visitors a day, contains advice on how to properly apply a security patch Microsoft has recommended people use to prevent the viruses returning.