Login to your Server Manager (http://localhost:8081/proxy-sadmsrv/bin/index)
From the list, click the server instance you wish the torrents to be blocked on (ie, server1)
In the tabs that appear across the top, select "Filters".
Make sure you have an information icon that says:
"The entire Server" was selected
If not, select it from the dropdown list.
Below that, enter a name of your block list in the box. Mine is called "blocked_list"
Click the "Create/Edit" button.
The Filter Editor will appear.
In the Filter content box, add the following:
You should have an alert that tells you the operation was successful.
Now, from the page that you are one, under the "Operate Filters" section, choose your "blocked_list" filter in the "URL Filter To Deny" dropdown box.
Files ending in .torrent will now be blocked. Unfortunately, there is no content inspection taking place so you wont be able to block torrents that do not have a .torrent extension.