You should review your credit reports annually (at least) to correct any errors. Also doing so can be a tool to help you spot identity theft.
The real free credit report site (for those in the USA), annualcreditreport.com, is provided by government regulation (so those that don’t believe in regulation would maybe rather use one of the sites advertising “free” credit reports). But I suggest using the government provided reports and I would suggest spreading the requests out during the year (you get 3 a year, 1 from each of the nationwide consumer credit reporting companies).
The site also has a large frequently asked question section including:
How do I request a “fraud alert” be placed on my file?
You have the right to ask that nationwide consumer credit reporting companies place “fraud alerts” in your file to let potential creditors and others know that you may be a victim of identity theft. A fraud alert can make it more difficult for someone to get credit in your name because it tells creditors to follow certain procedures to protect you. It also may delay your ability to obtain credit. You may place a fraud alert in your file by calling just one of the three nationwide consumer credit reporting companies. As soon as that agency processes your fraud alert, it will notify the other two, which then also must place fraud alerts in your file.
Where can I find out more about credit reports, my rights as a consumer, the Fair Credit Reporting Act and the FACT Act?
Please visit www.ftc.gov/credit