It's actually Defender Direct, also known by all the names you listed, and they're a licensed ADT dealer that is based in Indiana. Not a scam, just a contractor with ADT.
TerriS, you provide excellent information about checking web sites. But there is one thing many don't realize... TRACKING COOKIES. Facebook uses them as do many other web sites. Any company can find out who visits which site and send spam based on that. In my own case i was searching various window manufacturers and retailers web sites for a remodeling job I'm planning. Within 24 hours my e-mail was inundated with spam from every conceivable window company you can imagine. For the legitimate sites just click on the "unsubscribe" link usually provided and you won't hear from them. For others, it's a signal that your e-mail address is legitimate, and you'll continue to receive their junk.