Internet users around the world are being warned to take precautions against what could be the most crippling computer virus to infect the World Wide Web.
Not since the much-feared threat posed to the world's computers a year and a half ago by the so-called Y2K glitch has a threatened computer disruption received so much attention and advance warning.
This time, the threat comes from what is being called the 'code red' worm, a computer program known as a virus, that surfaced earlier this month, defacing websites with the words "hacked by the Chinese". The White House website was among those targeted.
Computer security experts and the FBI are warning the computer virus is poised to make a comeback as early as 0000 UTC Wednesday. But this time, it could be much more aggressive.
Ron Dick heads the FBI unit that goes after crimes in cyberspace. "There is reason for concern that the mass traffic associated with the worm's propagation could degrade the overall functioning of the Internet and impact ordinary users," he said.
Experts describe the virus program as a sophisticated and aggressive worm, since it is able to burrow into computer systems and the Internet. Any computer that runs on Microsoft operating systems could be vulnerable.
Paul McNabb, vice president of Argus Systems, an Illinois-based company focusing on Internet security, expects corporate and government websites will be most at risk - not the individual Internet surfer.
"It has the potential of being very damaging temporarily to certain sites that have been targeted," he said. "For most people, it will not affect them. The vast majority of people out there who are running their home machines will not see anything. Some of them might experience some downtime or slowness."
Earlier this month, the worm infected more than 350,000 computer systems and slowed the Internet by 40 percent. But the virus can be easily prevented with a protection device that users can download from Microsoft's website.
But not so easy to figure out is who is responsible for unleashing it into cyberspace.
"The fact that it seems to be attacking English language websites seems to point to the fact that it might be a non-English speaking attacker and people have pointed to China as a potential one, but we do not know that," said Mr. McNabb.
The FBI says it considers the code red worm a threat to national security since so much business and public service everything from banking to power companies rely on the Internet.