Corporate UK and the City of London are bracing themselves against a hackers' onslaught as part of a global protest against capitalism.
The Computer Crimes Unit (CCU) of the Metropolitan Police and the British Bankers Association (BBA) met this week to discuss the threat posed by the 'International Day of Action' on 18 June.
The CCU is also warning large companies in other sectors to shore up their cyber defences.
Businesses around the world will be targeted by demonstrations timed to coincide with a G8 meeting in Germany of the world's seven richest nations plus Russia.
As well as street demos by groups such as Class War and Reclaim the Streets, hackers will target banks and city institutions to try to bring the city to a halt.
Protesters plan to sabotage ATMs, while hackers will seek to prevent online banking and trading.
Class War's Web site said the action is in, "recognition that the global capitalist system is at the root of our social and ecological troubles."
A BBA spokesman would not reveal the counter measures to be taken, but said: "We take seriously any threat to disrupt orderly running of markets."
Peter Barnes is international operations director for business continuity group Survive!, members of which include the Bank of England and the London Stock Exchange.
He commented: "There are concerns that hackers will make a concerted effort on 18 June to undermine companies. We have advised our members to be extra vigilant and put network security people on standby. It is not just an issue of security, it harms reputations."
Neil Barrett, IT fellow for Bull Information Systems, said, "the easiest thing is for a hacker not to directly access a system but to stop access to a system by legitimate users."
He added: "It will not be high tech crime, but the prospect of it being widescale could cause chaos...this is door rattling. If you take simple security measures, they will move on to easier targets."
For more stories see this week's issue of Computing
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