When you joined your MLS you should have looked at their listing syndication policy. This is perfectly legal, and normal. Sometimes you can "opt out" of it, but frankly, sellers love seeing their listings get advertised on these sites. I use it as a selling feature in my listing presentations. But of course, when your listing gets put on those sites, they sell ad space to other agents. Maybe you need to talk to your managing broker about the pros and cons of listing syndication.