New variations of the e-mail virus disguised as a love letter which caused chaos around the world on Thursday spread to more computer users yesterday.
The United Nations headquarters' e-mail system had to be shut down for a period as a precautionary measure.
The latest viruses are disguised in one case as a confirmation for a gift order for Mother's Day which is on May 18th in the US.
Another version comes disguised as a joke labelled "Very Funny".
President Clinton, commenting on the viruses which have attacked e-mail systems and burrowed into the files on personal computers, said: "As we become more interconnected . . . we become more vulnerable to destructive forces that would seek, either from a bad design or to provoke chaos, to take advantage of it."
Mr Clinton said while he was "very gratified that the fundamental government system does not seem to have been affected here, we just have to keep working on it".
There were a few isolated incidents of the virus at the White House computers but operations were not affected, according to a spokesman.
But the State Department had to stop e-mail attachments coming into the unclassified section of its files linked to the Internet.
The CIA said the viruses were only a "minor threat".
The Army and Navy shut down their e-mail systems temporarily.
The Pentagon was working with virus protection companies to deal with the attacks, a spokesman said.
Other government departments had to turn off their e-mail servers for a time and use telephone and fax instead.
Employees were also warned in time against accepting suspect attachments to their e-mail.
Estimates of the cost to businesses of the love letter virus ranged from millions of dollars to $10 billion (€11.2 billion), mostly in lost worktime as firms were forced to close down their communications systems while experts worked to get rid of the virus.
Ford, Lucent Technologies and AT&T were among the large companies affected.
Experts said that, while the initial outbreak seemed to be slowing down, copycat versions were now surfacing.
At least five versions of the bug were spreading yesterday, according to a computer security company, F-Secure Corp in San Jose, California.
The Mother's Day version arrives as confirmation that the recipient's credit card has been charged $326.92 for a Mother's Day "diamond special".
The recipient is told to click on an attachment to print out the invoice but this releases the virus into the computer files.
The FBI has opened a criminal investigation into the virus attacks which are believed to have originated in the Philippines and mainly affect the e-mail programme and Internet Explorer browser of the Microsoft Windows operating system.
There have been renewed calls in Congress to tighten up laws against cyber-attacks.
