The exchange of information in Internet is made by the "client - server" model. A client sends a request (what files he needs) and a server sends a reply (required files). For close cooperation (full understanding) between a client and a server the client sends additional information about itself: a version and a name of an operating system, configuration of a browser (including its name and version) etc. This information may be necessary for the server in order to know which web-page should be given (open) to the client. There are different variants of web-pages for different configurations of browsers. However, as long as web-pages do not usually depend on browsers, it makes sense to hide this information from the web-server.
What your browser transmits to a web server:
- a name and a version of an operating system
- a name and a version of a browser
- configuration of a browser (display resolution, color depth, java / javascript support,)
- IP-address of a client
- Other information
The most important part of such information (and absolutely unnecessary for a web-server) is information about IP-addres. Using your IP it is possible to know about you the following:
- a country where you are from
- a city
- your providers name and e-mail
- your physical address
Information, Transmitted by the client to the server is available (accessible) for a server as environment variables. Every information unit is the value of Some variable. If any information unit is not Transmitted, THEN Corresponding Will Be empty variable (STI Will Be undetermined value).
These is Some Environment Variables:
REMOTE_ADDR IP address of a client
HTTP_VIA if it is not empty, then a proxy is used. Value is an address (or several addresses) of a proxy server, this variable is added by a proxy server itself if you use one.
HTTP_X_FORWARDED_FOR if it is not empty, then a proxy is used. Value is a real IP address of a client (your IP), this variable is also added by a proxy server if you use one.
HTTP_ACCEPT_LANGUAGE what language is used in browser (what language the page Should Be Displayed in)
HTTP_USER_AGENT? so called “a users agent”. For all browsers this is Mozilla. Furthermore, browsers name and version (eg MSIE 5.5) and an operating system (eg Windows 98) is also mentioned here.
HTTP_HOST is a web name servers
This is a small part of environment variables. In fact there are many more of them (DOCUMENT_ROOT, HTTP_ACCEPT_ENCODING, HTTP_CACHE_CONTROL, HTTP_CONNECTION, SERVER_ADDR, SERVER_SOFTWARE, SERVER_PROTOCOL,…). Their quantity can depend on settings of both a server and a client.
These examples of variable values is:
REMOTE_ADDR = 194.85.1.1
HTTP_ACCEPT_LANGUAGE = ru
HTTP_USER_AGENT = Mozilla/4.0 (compatible; MSIE 5.0; Windows 98)
HTTP_HOST = www.webserver.ru
HTTP_VIA = 194.85.1.1 (Squid/2.4.STABLE7)
HTTP_X_FORWARDED_FOR = 194.115.5.5Anonymity at work in the Internet is determined by what environment variables "hide”From a web-server.
If the proxy server is not used, THEN environment variables look in the Following way:
REMOTE_ADDR = your IP
HTTP_VIA = not determined
HTTP_X_FORWARDED_FOR = not determinedDepending on how environment variables are “hided” by proxy servers, there are several types of proxies
Transparent Proxies
They do not hide information about your IP addaddress:
REMOTE_ADDR = proxy IP
HTTP_VIA = proxy IP
HTTP_X_FORWARDED_FOR = your IPThe function of Such proxy servers is not the improvement of your anonymity in Internet. Their purpose is information Cashing, Organization of joint access to Internet of Several computers, etc..
Anonymous Proxies
All proxy servers, that hide a client IP address in any way are called anonymous proxies
Simple Anonymous Proxies
These proxy servers do not hide the fact That proxy is used, however They replace your IP With its own:
REMOTE_ADDR = proxy IP
HTTP_VIA = proxy IP
HTTP_X_FORWARDED_FOR = proxy IPThese proxies have the most Widespread among other anonymous proxy servers.
Distorting Proxies
As well as simple anonymous proxy servers these proxies do not hide the fact that a proxy server is used. However to IP clients address (your IP address) is replaced with another (arbitrary, random) IP:
REMOTE_ADDR = proxy IP
HTTP_VIA = proxy IP
HTTP_X_FORWARDED_FOR = random IP address
High Anonymity ProxiesThesis proxy servers is also calledhigh anonymity proxy". In contrast to other types of anonymity proxy servers they hide a fact of using a proxy:
REMOTE_ADDR = proxy IP
HTTP_VIA = not determined
HTTP_X_FORWARDED_FOR = not determinedThat means that values of variables are the same as if proxy is not used, with the exception of one very important thing? IP proxy is used instead of your IP addres.
Summary
Depending on Purposes there is transparent and anonymity proxies. However, remember, using proxy servers you hide only your IP from a web server, BUT other information (about browser configuration) is accessible!
