Love was in the air yesterday as the most damaging computer virus to date, the love bug continued to spread, mutate and take on new guises.

A new more virulent strain of the "I love you" worm virus or Mother's Day virus has appeared in Ireland. It deletes files that run applications and prevents a user from opening desktop programmes.

Some Irish companies shut down their servers, as a precaution, as new variations and strains of the love bug appeared yesterday.

RITS, a Dublin-based internet software security company, said the Mother's Day version is not as widespread in Ireland as the original which is thought to have affected nearly 100,000 computers here.

IBEC said the viruses had already cost firms millions of pounds in [NO ]both lost productivity and business.

If the situation continues, Mr Tommy McCabe of IBEC said the cost of worm viruses here would run into tens of millions.

Mr McCabe, director of the telecommunications and Internet division of IBEC, said a lot of companies had been unable to conduct e-business because of the virus and that authorities should come down hard on those responsible. The original virus crashed one Irish-based multinational's hard drives shutting down its international business arm on Thursday.

The new Mother's Day variation overrides and deletes BAT and INI configuration files central to the running of applications on a PC, and could render most of a user's desktop applications inoperable.

Once the attachment is opened the virus is activated and replicates by sending the e-mail to all addresses in the recipients address book.

The love bug has been called the fastest moving and most widespread computer virus to date. By yesterday evening the worm had spawned up to seven variants.

The other variants entice users to open an email by using subject lines such as "Fwd: Joke" and "Very Funny". A Lithuanian version of the virus has also appeared with the word "Susitikim" in the subject line.

Mr Dermot Williams, managing director at System House, an anti-virus software company, says the visual basic script in which the worm is written is a dangerously easy programming language to change.

Because the bug is so widely dispersed and easy to alter the number of variants appearing is just the tip of the iceberg, he says.