The survey conducted by Mori for global network services provider Dimension Data, revealed that most key decision makers have a misplaced trust in the ability of their companies to stave off the threat of hackers.
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Only 39 per cent of key decision makers responding to the survey, believed it was possible for their company to suffer an undetectable security breach.
In stark contrast, two thirds of IT managers admitted that the same organisation could be attacked and that they would be unable to detect the breach in the first instance.
Some 54 per cent of IT managers admitted their organisation did not have a security plan in place or were not sure if one existed, and that 62 per cent of bosses within the same organisation believed an incident response plan was in place.
Simon Boyle, Dimension Data's marketing manager, said: "If two out of three IT managers feel that they may not detect intrusions, that is worrying. We are talking about Britain's top public and private sector organisations here.
"They should be confident of the measures taken to protect their organisation from security breaches," he said.