A computer virus appears to have hit net search engine, Google, crippling its search service.
Net security firms have reported that the havoc seems to have been caused by a new variant of the MyDoom virus which is also targeting other search engines.
Google confirmed that a number of users in the UK and some US users were experiencing problems.
The search engine is one of the most popular on the net, dealing with 200 million global queries a day.
Huge index
First reports of the problems with the UK service started emerging at around 1530 GMT (1630 BST).
Instead of getting a page of results, some users in the UK, US and France have been confronted with a server error instead. Other net users have reported no problems.
Johannes Ullrich, chief technical officer from net security firm Sans Institute, told the BBC it appeared that the search engine was being overwhelmed by requests generated by the MyDoom virus.
Google is one of several search engines used by MyDoom to find valid e-mail addresses on the net. Past versions of the virus only searched a user's own computer or address list.
MyDoom uses a revolutionary new technique - I don't think we have seen this before
Graham Cluley, Sophos
The MyDoom-O variant spreads in the form of an e-mail attachment.
The attached message pretends to be from the user's net provider's or company's support team saying that their PC has been used by hackers to send spam.
Previous versions of MyDoom have launched distributed denial of service attacks (DDoS) on websites like Microsoft and software firm SCO.
Infected computers are used to bombard target websites with bogus data packages that utterly paralyse the sites.
"It does not appear to launch a traditional DDoS attack," said Graham Cluley, senior technology consultant for anti-virus firm Sophos, "and it is not just Google, but Altavista, Yahoo and Lycos."
"MyDoom uses a revolutionary new technique - I don't think we have seen this before," he added.
The new MyDoom variant searches infected machines for e-mail addresses, like other viruses before it.
But it also uses search engines to look for even more addresses in online forums and webpages.
High price
Google, based in Mountain View, California, announced its plans to float on the stock market in April.
On Monday, it announced it hoped its initial public offering (IPO) could raise as much as $3.3bn (£1.8bn), although no date for the IPO has been set.
This would give the California-based firm an initial market capitalisation as high as $36.25bn.
Google's web index is huge, carrying more than six billion items.
The phrase "to google" has entered popular parlance as a verb to describe an internet search.
But it faces growing competition from MSN and Yahoo, which are investing in search technology to try to win back web surfers.