Computer industry insiders fear that, while the criminals are at the cutting edge of technological developments, the police are ill equipped to fight digital crime, and the government is dithering over security measures which would allow companies to stop criminals in their tracks.

Chris Sundt, the head of the Confederation of British Industry's Information Security panel, believes "the problem is more serious than some people like to think."

And Jonathan Sowler, head of consulting for the London computer security company JCP, says computer crime is "becoming increasingly serious."

It is hard to work out exactly how much computer crime there is, but one estimate, by Mike Carlton, senior manager in Ernst and Young's fraud investigation unit, puts the figure as high as £10bn a year.

Criminals don't need passports, real or fake

The latest official figures for the UK are contained in the 1996 Information Security Breaches survey conducted among British companies by the National Computer Centre. It found one fraud of £650,000, out of only 661 organisations who replied out of 9,500 who were sent questionnaires.

It is in the USA that most computer crime is committed, and one bank found itself the victim of a spectacular heist.

A 30-year-old Russian, Vladimir Levin, is currently on remand in the US, accused of transferring more than £6.2m ($10m) out of Citibank accounts all over the world. He was arrested in 1995 at Stansted airport in England, and extradited to the US. Citibank have managed to recover all but £250,000 ($400,000) of the cash, but they are still trying to work out how the money was stolen.

If the Citibank raid is the biggest computer crime yet reported, there are plenty of smaller cases, which could give a truer picture of the problem.

Most involve stolen credit card numbers, and it is companies selling software over the Internet who are the main victims: "We had a week in which we had more fraud than legitimate sales," said William McKiernan from the American online store Software.Net. At a similar site, Buynow.com, the fraud rate hit 20% early in 1997.

There are plenty of other examples:

• The FBI are still investigating the theft of 50,000 credit card numbers downloaded from MCI's computers and used to charge more than $50m worth of goods in 1995.
• Five teenagers from Minneapolis stole between 20 and 25 credit card numbers and used them to order goods over the internet. They were caught however when they had the goods delivered to their own home ...
• Carlos Felipe Salgado who was arrested by undercover FBI agents at San Francisco airport in May 1997 after trying to sell them a disc with more than 100,000 credit card numbers on it. He had got them by hacking into various computers.
• Kevin Mitnick, a well known US hacker, who was caught with 20,000 credit card numbers. He is currently in prison awaiting trial on hacking charges but insists he never used the credit card numbers for personal gain.

Perhaps the most serious computer crimes committed took place when more than 40 banks and other financial institutions in London and the US were targetted by gangs who threatened to destroy their computer systems unless huge ransoms were paid.

Although hard facts about the attacks are hard to corroborate, because of the companies' natural reluctance to give details of how much they lost, its been widely reported that up to £400m may have been paid out in ransoms.

And those in the computer industry in Britain who are worried about online crime say their efforts to fight back against the criminals are being hampered.

Not only are the police ill equipped and under-resourced to take on the digital criminal, but government fears about encryption are preventing the industry putting really secure barriers in place.