Were you a LinkedIn user in 2012 or earlier? Email addresses and passwords on more than 164 million users were stolen in that massive hack. Last week, 117 million credential were leaked. Has your account been breached?
I checked all my addresses and one had been breached by Adobe (2013), Boxee (2014) and now the current Linkedin “thanks” guys. Guess we know who really needs password protection!
What you should do if you're concerned is to log into your "pwned" account(s) and change your credentials.