Does anyone know the site for free credit reports when the gov. messed up?

♥countrygal♥ asked:

The gov. sent out mailings with peoples social security numbers typed on the front. They then sent out letters to everyone giving them a free site to check their credit because of identity theft. I can’t find the letter and need the web site. Also was there a specific code or anything you needed to use so they knew you were one of the people to receive the error mailings?