Once a name has been registered is it possible to be protected against similar names being used?

Registering a domain name does not protect you against similar registrations. If you are damaged by the assignment of a domain to others, you can use the law to help your case, or you can set up a dispute procedure and activate one of the alternative means of resolving disputes (arbitration / reassignment) as set forth by the Regulations for assigning and managing .it domains.