How to block Utorrent in wifi modem

Torrent is designed to get around any blocking. It can even be configured to bypass a corporate proxy using https. You can block lazy people by blocking some of the common ports but all they do is change those and some torrent clients automatically change them if they detect a attempt to block the client.
You can try to block the sites with the seeds but there are many ways to get these.

It is like the opendns solutions they only stop the person who does not have the skills to use google to search which is only you most naive users.