Install Hitch Guard over your hitch and push it as far back as it will go. Secure with wire ties included - you can use 1 or 2. Pull the wire ties tight enough indent the foam about 1/8". Cut off the excess tie.
If you are concerned about theft use some adhesive on the hitch along with the ties.
The Hitch Guard should not interfere with any normal towing functions. To be sure have someone walk alongside the trailer briefly.