Some folks use Lifelock but you can basically do everything they do for free. I recommend to my clients that they put a credit freeze on all three credit reports, transunion, experian, and equifax. Keep the PIN numbers in a safe place. Check your credit reports every 4 months, looking at one report, then 4 months later the second one, then 4 months later the last one.
Dont put your social security number on ANY document unless it is applying for credit, a job or a tax document, or possibly insurance. So many doctors use boilerplate forms and they always seem to ask for the SSN. Leave it off. They most likely don't need it and doctor's files seem to get hacked all the time.
Some folks use credit karma for monitoring and some folks...who have been victims of doctor office hacking etc, just use the one offered in the informing letter.