Proxy Server Basics
 by: Terry Steele

Proxy server is the software installed on some network server. The main purpose of this software is to relay traffic between two network hosts (client and server), sometimes this software does some data caching (usually this is performed by HTTP proxies). If your browser is configured to work through the proxy server then all your network traffic will go through that proxy server.

The main purposes of proxy servers:

* Transfer speed improvement (in case of caching proxies). You may use your ISP's proxy to access the internet ?usually you have better connection to your ISP's proxy than to other hosts, if this proxy has the resource you requested from the internet you will get a copy of it from proxy (from its cache).

* Security and privacy (for HTTP). Anonymous proxies hide information about your computer in the request headers, so you can safely surf the net and your information will never be used in any way.

* LAN interconnection (or LAN to WAN connection). Sometimes you experience some problems while accessing the server located in the other network (for example in the internet).

How to setup your browser for proxy access:

To set up your web browser follow the intructions below. You have to replace and with the proxy address and its port. It is preferred to use an IP address instead of proxy's hostname to avoid the name resolution that your browser will perform in case of hostname usage. Examples:

Microsoft Internet Explorer 5.0 or later

1) Choose the Tools menu.
2) Select Internet Options.
3) Select Connections.
4) Select LAN Settings.
5) Check "Use a proxy server".
6) Enter in the "Address" text box.
7) Enter in the "Port" text box.
Press "Apply".
9) Press "OK".

Netscape Communicator(Navigator) v4.0 and higher

1) Choose the Edit menu.
2) Select Preferences.
3) Select Advanced->Proxies.
4) Check "Manual Proxy Configuration".
5) Click "View...".
6) Set the appropriate fields to and values, it depends on proxy type you want to use.

There are 3 levels of HTTP proxies:

* Level 1: High anonymous (elite) proxies. Such proxies don't change request fields and look like real IP. You real IP is hidden of course. People that administrating internet servers will think that you are not using any proxies.

* Level 2: Anonymous proxies also don't show your real IP but change the request fields, so it's possible to detect that proxy with log analyzing. Nothing really matters, but some server administrators restrict the proxy requests.

* Level 3: Transparent proxies (not anonymous, simply HTTP) change the request fields, also they transfer real IP. Such proxies are not applicable for security and privacy while surfing on net. You can use them only for network speed improvement.

How to know the level of the proxy?

Forum Proxy Leecher (fpl.my-proxy.com) is an an intelligent proxy leecher that can get proxies from forums, however it's also a good proxy tester to check the level of the proxies. It's especially useful if you want to test a great amount of proxies. Download it at http://fpl.my-proxy.com/FPL_setup.exe.

Proxy Chain

You can use several proxy servers simultaneously. It is called "cascaded proxies". Use the following settings in your browser: http://proxyA:portA/http://proxyB:portB/. But you may expect some speed loss in this way.

Some Hypertext Transfer Protocol (HTTP) information

HTTP is a high level (application level) protocol which provides the speed you need and quality data transfer. HTTP based on request/response mechanism. The requesting application (client) establishes the connection between you and server. It sends the request to the server in the following form: request method, URI (uniform resource identifier), protocol version, MIME (Multipurpose Internet Mail Extensions) coded message witch contains service information, client information and sometimes message body. Server processes the request and answers with a message which contains status string followed by the MIME coded message.

We can see that client sends to server the great amount of information including the information about itself. This information we are interested in ?it is called request fields. The header of request consists of the following fields (only those we are interested in): Pragma, Forwarded, Client IP, Via, X-Forwarded For, Proxy-Connection, Remote Address. These fields cause the privacy leak. Elite proxies correct this fields to bring you maximum privacy.

SOCKS proxies

SOCKS is a protocol that relays TCP sessions at a firewall host to allow application users transparent access across the firewall. Because the protocol is independent of application protocols, it can be (and has been) used for many different services, such as telnet, ftp, finger, whois, gopher, WWW, etc. Access control can be applied at the beginning of each TCP session; thereafter the server simply relays the data between the client and the application server, incurring minimum processing overhead. Since SOCKS never has to know anything about the application protocol, it should also be easy for it to accommodate applications which use encryption to protect their traffic from nosey snoopers. No information about the client is sent to the server. Thus there is no need to test the anonymity level of the SOCKS proxies.

About The Author

Terry Steele, the webmaster of My-Proxy (www.my-proxy.com), home of free security knowledge, online security tools and proxy softwares.