Nearly 12 million Americans were victims of identity theft in 2011, an increase of 13 percent over 2010, according to a report released Wednesday by the research firm Javelin Strategy & Research.

The rise in the use of smartphones and social media by incautious consumers fueled the increase in identity fraud, and 2011 was a year of several big data breaches too, Javelin said.

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With the rise in credit card monitoring and more sophisticated policing by credit card companies, identity thieves are increasingly targeting users of smartphones and social media, where consumers have a tendency to be less cautious, experts say.

The number of people whose information was accessed in a data breach increased by 67 percent in 2011, largely due to some very high-profile thefts, such as the attacks on Sony Corp.'s PlayStation network in April.

Someone whose personal information is taken in a data breach is 9.5 times more likely to become a victim of identity fraud, Javelin found.

One heartening finding was that dollar losses by consumers remained stable last year despite the increase in the number of victims. Credit card issuers' policies on fraudulent transactions -- a $50 limit on losses, which is often waived -- and quicker detection has limited out-of-pocket costs to consumers, said Javelin founder and president Jim Van Dyke.