If your Social Security number was included in the nationalpublicdata.com breach, you may want to put a fraud alert on your credit. Notifying one of the three agencies will automatically work for all three:

https://www.experian.com/fraud/center.html

Likewise, you can put a credit freeze on your files at all three agencies, but you need to notify them individually. (If you need to apply for credit you can temporarily thaw your file.)

https://www.experian.com/freeze/center.html

https://www.transunion.com/credit-freeze

https://www.equifax.com/personal/credit-report-services/credit-freeze/