I now realize I asked the wrong question.
We do allow guests to view the Moodle page. However, students can still log in with their username and password from the university, even though they are not registered for the course. So I have students that are "logging in" to Moodle, then viewing the homework problems. They are being given an account dynamically and have student status. Is there a way to keep these individuals which are not enrolled or specifically added to the Moodle course out of Webwork?
I should also mention -- the easy way to identify them is by a lack of section name in WW.