Not really, no. Because although you can restrict your front page to only show specific courses and although you can restrict users from accessing courses (ie being able to enrol in them) there is nothing to stop a user who knows the link going to yourmoodlesite.com/course/index.php which is the list of all the courses on the site visible without a log in. (Try it with any Moodle site that has a visible front page)
People might say there are ways around it by changing permissions to view hidden courses etc etc but it's a lot of work and I'm not convinced it's effective.
You can of course make it harder to find courses, so you don't show any courses on the front page and then if Joe Schmo is enrolled in only two courses and the Dashboard is the default page after login then he will only see those two courses he is enrolled in , and hopefully won't go searching for others.