Got called on a number that is not listed and few people have and never give out (online or to retailers). Called back from a central exchange and got a marketing records so definately a bulk dialer.
Do not call back it will get you nowhere. If they are a scam they now have your number to sell to others, it is best to ignore. If you dont answer they will give up.
Update:
DEFENDER Direct marketing - "Protect Your Home" Security. Pushing a "FREE" security system if you just let them put up a sign, or the says FBI wants you to put up a sign and get a "FREE" security system.
Telemarketing, will offer you various things but others report "bait and switch" like marketing tactics to get a installer to come to your home and hardsell/upsell you.
Do not answer or call back. If you want ADT Security call ADT directly. You can verify yourself but this company does not appear to participate with the Better Business Bureau.
I got a call from this number, i didn't answer. But there was no message left. I decided to look up the number on white pages, and guess what? They have no record on the number. Why would a telemarketer not have a legit number?