Proxy server of this type represents (from user's point of view) a usual web-page, very similar to pages of search engines. But instead of search phrases you should type into an input field the URL of that site which you want to look at. Then, having pressed the "Submit" button or "Go", you will get onto page, which URL you have specified to a CGI proxy. But address of this page (in the address line) from the point of view of your computer will be another, something like
http://www.cgi-proxy.com/http/www.your-url.com/path/ for example:
Using such proxy servers, you can anonymously surf all over the Internet, without changing settings of your browser and without using any additional programs.
CGI proxy supports HTTP and (sometimes) FTP protocols.
As for anonymity, CGI proxies are the same, as the HTTP proxies:
1. Transparent - these proxies are not anonymous. They, first, let a web server know, that there is used a proxy server, and, secondly, "give away" an IP address of a client.
2. Anonymous - these proxy servers let a remote computer (web-server) know, that there is used a proxy, however, they do not reveal an IP address of a client.
3. Distorting - unlike the previous type, they transfer an IP address to a remote web-server, however, this address is a phantom: randomly generated by a proxy-server or any fixed (not your) IP. So, these proxies distort your IP address from web server's point of view.
4. High anonymity - they do not send your IP address to a remote computer. Moreover, they do not inform that there is used any proxy server! So, a web-server "thinks" that it works directly with a client.
For use of a CGI proxy you do not need to change your browser settings, to install additional programs or to make something else more complex. It is enough, if one opens a web page of CGI proxy in a browser, enters a required URL into the address field and press the "Go" button.
The disadvantages in usage of the CGI proxies are presence of additional advertising (which adds a CGI proxy itself, they simply exist at the expense of such advertising), a limited FTP support (not always supported) and sometimes a CGI proxy do not allow to view pictures.
Some CGI proxy could be installed as a proxy in a browser, but it is rather an exception than a rule.
Creating a chain from free web anonymizers (CGI proxy) is a very simple thing. It would be enough in one CGI proxy to type an address (URL) of another CGI proxy and to press "Go". The same way it is possible to use 3d, 4th, 5th... proxy-servers. In last proxy of a chain just type URL of a required site and browse a site you need. That is all!
Thus, it is possible to organize into a chain any number of CGI proxies.
CGI proxies could be combined with other types of proxy servers (HTTP, SOCKS). However, they should be the last ones in this chain:
You can organize them this way:
SOCKS proxy > > > > HTTP proxy > > > > CGI proxy
HTTP proxy > > > > CGI proxy
SOCKS proxy > > > > CGI proxy
And you can not do so:
CGI proxy > > > > SOCKS proxy
SOCKS proxy > > > > CGI proxy > > > > HTTP proxy
CGI proxy > > > > HTTP proxy
There is no problem. If you have an Internet access (you can view web pages), you can use a CGI proxy. You also can unite several HTTP / SOCKS proxies into a chain and at the end of this chain to use a CGI proxy. Moreover, you can at the end of this chain create one more chain - from CGI proxies!
Alas, with standard way this could be hardly done.
Unlike other types of proxy servers CGI proxies have considerably wider abilities as for information filtering. They can:
Thus a system administrator viewing server logs with analysis purposes can not determine what server you have reached (www.sex.com or www.altavista.com).