A few weeks ago I started receiving notices that my SSN was detected online by the identity monitoring company I use. I guess this is the source of that.
Around a year ago my identity was stolen (new CCs opened in my name). At that time I froze my credit on all 3 of the agencies. It's easy to turn it off/on with a switch so I have left it frozen. Its a good feeling knowing that no one can open a new CC in my name.