NEW YORK — When it comes to identity theft, most people think they're especially vulnerable when they're working on their computers or when fraudsters hack into big databases and steal card numbers.

In fact, consumers are far more likely to be victimized if their wallet, checkbook or credit card is lost or stolen, according to a new study released by Javelin Strategy & Research.

The research group, which is based in San Francisco, also found that as financial institutions and retailers have improved their in-store and online security, ID thieves have turned to more traditional channels of theft, especially the telephones and the mail.

While the incidence of ID fraud through in-store and online purchases declined in the latest survey, conducted last October, from a similar study in 2006, the portion of fraud stemming from mail or telephone purchases jumped to 40 percent from 3 percent.

Identity theft occurs when someone uses an individual's personal identifying information, such as a credit card number, without the person's permission to commit fraud or other crimes. Javelin's study covered incidents ranging from a one-time misuse of someone's credit card number to the takeover of a person's account or creation of new accounts in a person's name.

James Van Dyke, president of Javelin, said in an interview that many Americans are too trusting on the phone.

"In a typical situation, unsuspecting consumers receive phone calls from parties claiming to represent nonprofit organizations, billing institutions or other financial institutions," Van Dyke said. "Far too many of these consumers provide the callers with personal information, such as Social Security numbers, bank account numbers and credit card numbers."

With that information, criminals can open accounts in the victim's name, empty existing bank accounts, even buy cars or homes.

While the Javelin study found that overall ID theft was falling, it also found that the cost for consumers to resolve the resulting fraud was rising.

The latest study indicated that 8.1 million Americans were victims of ID fraud in 2007, down from 8.4 million a year earlier and 10.1 million in 2003.

The total cost of ID fraud also dropped, to $45 billion in the latest study from $51 billion a year earlier and $56 billion in 2003.

Van Dyke attributed the drop to a variety of defensive steps by consumers and institutions, including "greater consumer vigilance and awareness, improvements in systems and practices by companies that manage personal information . . . and consumers more frequently updating spyware and antivirus software."