UDGER.com is a leader in the detection browsers, mobiles, tablets, Smart TV .., also provides info about IP addresses (proxies, VPN, Tor exit nodes ..). Since 2005 the Udger team provides services to detect of user agent strings. This project was called user-agent-string.info and was until 2014 freely available. During 2014 they extended the reach of their components and created Udger.com. The company updates their database several times a day to detect more strings.
To block TOR traffic or any anonymity service out there is not an easy decision. Any product manager of online services faces this dilemma sooner or later: let users onboard in my service as simple as possible so they can test my product or harden the conditions for registration and therefore drive away potential customers.