There are different types of circumvention applications, each using slightly different techniques. There are both public and private external proxies that can use both HTTP and HTTPS (see proxy.org for a large database of public proxies). Private proxies are often set up on unclassified IP addresses, such as home computers, with applications like PHProxy or CGIProxy. Remote access applications, like MS RDP or GoToMyPC, can have legitimate use, but because of the associated risk, these should be managed. Most other circumventors, such as Ultrasurf, Tor and Hamach,i don’t have business uses.