What it does: Prevents anyone from looking at your credit report, except for companies that already have a financial relationship with you, certain government agencies, and other exempt entities. Lenders who can't pull your credit report aren't likely to grant new credit to someone else in your name.

What it costs: Typically $30 a person to file at the three major credit bureaus, but fees range from free to $60, depending on state law, each time you freeze or unfreeze your credit report yourself. If you're a victim of ID fraud, it's usually free. Protection companies don't generally offer this service, but one that does charges $45.

Should you do it? Yes, even if your identity has not been compromised, to shut out ID thieves before they can cause credit damage. Remember, though, that while the freeze is on you can't open any credit accounts, and landlords, prospective employers, utilities, and others can't assess your credit history when considering a new relationship unless you unfreeze your report or obtain temporary access for specific parties.

Where to get it: You can freeze your records at each of the three major credit bureaus, Equifax, Experian, and TransUnion. Experian lets you place a freeze using the Internet; the other two require a written request by U.S. mail.

Beware: Despite its name, TrustedID's IDFreeze service is not a security freeze at all. It's a fraud-alert placement service. The company does offer security freezes at all three bureaus under its CreditLock service, which costs $44.95-significantly more than may be required by most state laws or charged by the bureaus directly.

Equifax and TransUnion let you lock and unlock your report anytime. But this is not an official security freeze. It's an add-on to their credit-monitoring services, which cost $11.95 to $14.95 a month. And the lock stays only as long as you subscribe to the service.

This article was also published in Consumer Reports Money Adviser. Subscribe now to get more expert financial advice you can trust.