SPENDING on internet security is expected to soar over the next year and beyond in the wake of last week’s outbreak of the Sobig.F computer virus.

Big companies and software firms are preparing themselves for a surge in computer security budgets amid fears of systems breakdowns. Small businesses also voiced concern about rising costs of security.

Last week Sobig.F, a virus that exploits weaknesses in Microsoft software, clogged the internet as it triggered e-mails to everybody listed in an infected computer’s address book.

David Weymouth, chief information officer at Barclays Bank, said that “IT security is a growing part of our overall IT spend”, at a time when corporate computing budgets have come under pressure.

He added: “For big companies this has now become a big issue. What happens if somebody knocks one of your systems down? Companies are hugely dependent on computing, even for things like e-mail.”

Barclays is one of Britain’s biggest spenders on IT. A bank of its size spends £750 million a year on information techology, and computer security represents “a single-digit percentage” of that — suggesting that the security element is as much as £50 million a year.

BT, the telephone giant, said that it was coming under pressure from its customers to spend more.

Yesterday its internet arm, Openworld, reported an increase of 900 per cent in the number of customers requesting protection for their e-mail accounts. The total number of queries was “in the thousands”. Nick Truman, head of customer security for BT Openworld, said: “If we continue to see problems like this, then we would have to invest more.”

Although BT does not charge for e-mail protection — which it does not provide as standard — it has to license the technology from the software developer Brightmail.

KPMG, the audit and consulting firm, is also preparing for increased security related spending by its customers. Rick Cudworth, a partner responsible for internet security, said: “Today security accounts for 2 to 4 per cent of IT budgets; we think this will grow to between 5 and 10 per cent over the next three years.”

Companies in the IT security sector are reporting a boom in sales. SurfControl, a British e-mail filtering company, is expected to reveal shortly that it has achieved a rise in sales of 35 per cent to $73 million (£46million) in the year to June. Analysts expect a 28 per cent improvement to $94 million for the present year.

Ian Spence, a technology analyst at Granville Baird, said: “Spending on security has been highly resilient during the IT sector’s recent downturn. It is clearly now a growth market.”

That will increase the pressure on smaller companies. Anti-virus software typically costs £25 a computer, while an internet firewall can easily cost several thousand pounds.

Stephen Alambritis, of the Federation of Small Businesses, said: “There is a real fear that small businesses are being forced by the software industry to buy products they do not necessarily need.”