The monitoring system developed by China is not confined to the Great Firewall, monitoring is also built into social networks, chat services and VoIP. Private companies are directly responsible to the Chinese authorities for surveillance of their networks to ensure banned messages are not circulated. The QQ application, owned by the firm Tencent, allows the authorities to monitor in detail exchanges between Internet users by seeking certain keywords and expressions. The author of each message can be identified by his or her user number. The QQ application is effectively a giant Trojan horse. And since March 2012, new legislation requires all new users of micro-blogging sites to register using their own name and telephone number.