Internet security companies reported one of their busiest days in the Republic yesterday as worried customers sought reassurance in the face of the "Code Red" worm.

The worm, which targets English language websites that run on certain Microsoft software platforms, was set to infect global computer systems from 1 a.m. today. Following warnings issued yesterday by Microsoft Ireland and extensive media coverage of the dangers posed by the worm, many companies contacted security specialists.

Mr Alec Florence, head of Priority Data Group, said hundreds of companies contacted the Dun Laoghaire-based firm to see if they were at risk. "People are working unbelievable hours today and, when I left the office, there were still 35 calls backdated which staff were going to deal with," he said.

Mr Florence said most companies which contacted the firm had already installed a software patch made available by Microsoft and he did not expect Irish companies to be hit hard by "Code Red".

Another internet security firm, Enthropy, said there would undoubtedly be some problems tomorrow, but the media exposure had been so great there could not be many companies unaware of the worm.

"It really shouldn't be a problem but there are always exceptions. Maybe the systems administrator has gone on holiday," said Mr Conall Lavery, managing director of Enthropy.

The "Code Red" worm targets websites which run on ISS Web server software powered by Windows NT and Windows 2000 software platforms.

It should not affect most home computer users who do not generally run their own servers.

The worm scans the internet, identifies vulnerable systems and infects these systems by installing itself.

Mr Joe Macri, country manager Microsoft Ireland, said yesterday immediate action was required to combat the threat. Any companies which become infected should reboot their computers to rid their machines of the worm and instal the software patch as directed, said Mr Macri.