The company, which is a unit of chipmaker Intel Corp, disclosed the flaw in a message to customers on its website Wednesday.

McAfee spokesman Ian Bain said t least one customer had fallen victim to such an attack, which leveraged a flaw in a service offering known as McAfee SaaS for Total Protection.

The web-based service protects customers from viruses hidden in emails and websites. Bain said the flaw was in a piece of software that McAfee customers install on their PCs to enable them to use the service.

While the flaw could enable hackers to send spam from machines of McAfee SaaS for Total Protection customers, it does not grant them access to data on an affected PC, Bain said.

He said that the company's engineers were working to fix the bug and expected to have it fixed on Thursday.

In April 2010, a glitch included in a regular release of McAfee's anti-virus software mistakenly identified part of Microsoft Corp's (MSFT.O) popular Windows XP operating system as a virus, triggering personal computer outages at many of its customers, including more than 100 large corporations.

(Reporting by Jim Finkle; Editing by Matt Driskill)

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