An anonymizer or an anonymous proxy is a tool that attempts to make activity on the Internet untraceable. It is a proxy server computer that acts as an intermediary and privacy shield between a client computer and the rest of the Internet. It accesses the Internet on the user's behalf, protecting personal information of the user by hiding the client computer's identifying information such as IP addresses.[1][2][3] Anonymous proxy is the opposite of transparent proxy, which sends user information in the connection request header.[4] Commercial anonymous proxies are usually sold as VPN services.