The tools put in place to filter and monitor the Internet are collectively known as the Great Firewall of China. Besides the usual routing regulations that allow access to an IP address or a particular domain name to be blocked, the Great Firewall makes large-scale use of Deep Packet Inspection (DPI) technology to monitor and block access based on keyword detection. The Great Firewall has the ability to dynamically block encrypted connections. One of the country's main ISPs, China Unicom, automatically cuts a connection as soon as it is used to transmit encrypted content.