Barracuda Web Filter (Model 210) problem using https

Hello,
I have a barracuda Model 210 web filter.
I plainly use this as a web filter in our small office so they can't access social networking media and other sites that is eating up a lot of bandwidth that will hinder our VOIP performance.
Our network is setup as a domain and the firewall works but when a user types https://www.domain.com/, though the domain is blocked, it will let them access it using https.
I tried blocking https and to no avail.
Thanks in Advance!
Chris P.
