A Proxy (proxy server) is a server that acts as mediator between the client (the computer of
a user) and server (the computer on the other ends of network connection
on which the information requested by the user appears for example web server site.)
When clients request data from an Internet resource,traffic goes from your web browser/application first through the proxy
before it reachs the requested sources and back through the proxy.
Then the proxy will transmit the data (information) to you.
Proxy server are very often used to improve the performance of a network traffic
by using its capacity to store informations that has been used by many internet users.
For example when one person visits an internet site a copy of the information is stored
on the proxy server.
When another person afterwards visit the same Internet site
then he gets information immediatly because the data has been previosly stored.
Such a process of storing of information on proxy server is called cache.
The advantage of the proxy server cacheing method is that the network must less frequently make
contact with the original Internet site. The disadvantage is that the shown information is
not the most recent available.
However old cache that remains on the server are frequently deleted based
on the server administrators rules (time, age, size, access....) that says when the information
is to be removed from the servers cache.
Proxy servers may also be used to bypass restrictions and limitations that the owner
of the internet resource has set for users from specific country, region and users that fall into
specific ip address ranges.
For example if the website owner (webmaster) for whatever reason blocks access to the visitors
from some countries the visitors from blocked country could use an open free proxy server from
another countries and override the restriction.
Unfortunately the abuse of open proxy servers has become a common problem in the last couple of years.
As with many other things in life,proxy server are not exempt from the fact that everything positive has negative side.
The people with malicious intent use frequently open free proxy servers for spamming, flooding,
fraud and other unwanted activity.
Open Proxy Server
Open proxy servers are public proxy servers which permit connections by any client anywhere in the world
with any Ip adress.They is free and could be used by everybody on the Internet.
HTTP proxy server are sorted in 3 groups:
- anonymous proxy server
- Elite
- Simple HTTP Anonymous proxy server
- transparent (non anonymous)proxy server
- gateways
Anonymous proxy servers do not show your ip address to the website that you requested information from.
Instead of your ip address the website should see the proxy servers ip.
The fact that anonymous proxy servers hide information about your computer means that you may
safely surf the net because information about you will be not be sent.
Every http proxy server sends small pieces of information to the web server that tells more about
how the connection has been made.This kind of information is called a variable.
- HTTP_VIA, HTTP_USER_AGENT_VIA, HTTP_FORWARDED - these variables tell the web server that a proxy has been used
- HTTP_CACHE_CONTROL, HTTP_CACHE_INFO - These variables contain information about the cache of the proxy server.
- HTTP_CONNECTION: Close or Keep-Alive - the connection type "close" demonstrates the use of a proxy server.
Non proxy server request use Keep-Alive type of connection.
Anonymous proxy server are grouped (on the basis of "headers" that they send to the website) into
elite and simple http proxy server.
- Elite proxy servers (aslo called Level 1 and Level 2 proxys) do not send any typical proxy variables
and it looks to a website as if you are not behind a proxy.
- Simple HTTP Anonymous proxy servers hide your ip address but the presence of some variables
tell the website that you are behind a proxy server.
From the view of anonymous surfing there is not really any difference between Elite and simple http proxy servers
but sometimes the use of Elite proxy servers is required. Usually when the webmaster of website
tries to block proxies he checks each request for typical proxy variables.If they are found
access could to the site could be blocked.
Transparent or non anonymous proxy server are in some cases usefull for increasing the speed
of your connection but because they forward your real ip address to the webserver they are
not applicable for anonymity, security or privacy while surfing the net.
A Gateway proxy server is a server that points to another ip address (gateway) and then transmit
information to you. Assuming the gateway is anonymous then your ip address will be always
hidden.
Example:
proxy server 217.218.42.1--->
proxy server 217.218.42.2--->
proxy server 217.218.42.4--->217.218.42.0-Gateway--->transmit information --->Your PC
proxy server 217.218.42.7--->
proxy server 217.218.42.9--->
