The Republic has a particularly high rate of computer fraud, according to Mr Dan Quealy, the director of Ernst & Young's security and technology solutions team.

Mr Quealy, an American security specialist who worked previously in Ernst & Young's Chicago office, said the Republic had 20 cases of computer fraud in the past year, whereas in Chicago, he'd only seen six cases in three years.

While the difference could be due to an increased frequency of computer fraud in general, Mr Quealy suggested other reasons could be that the State has a successful software industry with a young, well-informed technology workforce; that the increase in redundancies is causing revenge attacks; or that it may be easier to hack into company digital telephone exchanges in the Republic.

A recent Ernst & Young survey of the attitudes of Irish companies towards security revealed a low awareness and level of concern about computer security issues. Only 33 per cent of Irish respondents expressed concern about internal attacks on systems, compared to 41 per cent globally.

Some 33 per cent of Irish respondents also ranked security projects as a low priority - compared to only 14 per cent of their global counterparts. In a recent FBI survey, 90 per cent of respondents - mostly large corporations and government organisations - reported attacks on their computer systems.

Companies that suspect any form of computer fraud or believe a company computer might contain incriminating files should act carefully, said Mr Andy Harbison, director of Ernst & Young's security and technology solutions team.

Evidence - both files and digital trails that indicate what a suspect might have been doing on a PC - is often inadvertently destroyed if a company starts trying to examine a suspicious PC.

Companies should not turn on the PC if it's off, or turn off the PC if it's on. Then, they should appoint a point of contact for computer forensic investigators, whether from the Garda, which has its own team, or a private company. "You need someone who can put the information that is retrieved into context," said Mr Harbison.

Forensic investigators will immediately pull the hard drive out of the PC and make a copy of it, and then a backup of that copy, said Mr Quealy. The second copy is examined so that primary evidence is not altered.

Although some people try to erase evidence using specially-designed programs, often incriminating fragments of evidence can still be found as most people are too inexperienced to use them properly, said Mr Harbison.

He also offered examples of several Irish computer fraud and crime cases, ranging from an employee who downloaded pornography onto a colleague's computer to a chief executive who was passing sensitive information back to colleagues at another company.