Yahoo Inc has said it has contained a malicious programme aimed at millions of people who use its e-mail service, which ranks as the world's largest.
The worm, dubbed 'Yamanner,' infected a recipient's computer as soon as the toxic e-mail was opened.
It then scanned contact lists for additional targets, according to security software maker Symantec Corporation.
Sunnyvale, California-based Yahoo said on Tuesday that "a very small fraction" of its more than 200 million e-mail accounts were infected on Monday when the problem was first identified.
The worm didn't affect the e-mail service, which remains in its test, or 'beta,' phase.
"We have taken steps to resolve the issue and protect our users from further attacks of this worm," Yahoo spokeswoman Kelley Podboy said.
"The solution has been automatically distributed to all Yahoo Mail customers, and requires no additional action on the part of the user."
As a precaution against variations on the Yamanner worm, Yahoo advised its e-mail users to update their anti-virus programs and block all incoming correspondence from av3@yahoo.Com.
The worm arrived in the form of an e-mail containing JavaScript and contains the words "New Graphic Site" in the subject field, according to Symantec, the maker of Norton anti-virus software.
{{/usCountry}}The worm arrived in the form of an e-mail containing JavaScript and contains the words "New Graphic Site" in the subject field, according to Symantec, the maker of Norton anti-virus software.
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