After the massive security leak of 143 million Social Security numbers at credit reporting agency Equifax, the company has announced that it will not charge for "credit freeze" requests for the next 30 days.
Here's where you can sign up for a credit freeze at the big three reporting agencies :
https://www.freeze.equifax.com/Freeze/jsp/SFF_PersonalIDInfo.jsp
https://freeze.transunion.com/sf/securityFreeze/landingPage.jsp
https://www.experian.com/ncaconline/freeze
Note that many states normally allow credit reporting companies to charge a fee for placing a credit freeze on your account. For example, in California, the fee is $10.