1. PROXY SERVER
INTRODUCTION
 PROXY - A proxy act as an intermediary agent between its
client and the server which they want to access ,performing
function directed towards a variety of purposes like security,
caching etc .
 As the name proxy it means server
which fills up or acts and provides functionalities of some other
server .
 PROXY SERVER – A server that sits between a
client application, such as a Web browser, and a real server. It
intercepts all requests to the real server to see if it can fulfill the
requests itself. If not, it forwards the request to the real server.
A Proxy server is a computer
that offers a computer network services to allow clients to make
indirect connections to other network services .
 It also act as an intermediary between web
server and its clients
 A proxy server is a server ,a computer system
Or application program that acts as an intermediary from clients

2. Seeking resources from other server . A client connecting to the
proxy server such as file , connection, webpage or other
resources available from different servers.
 A proxy server may optionally alter the client's
request or the server's response, and sometimes it may serve
the request without contacting the specified server. In this case,
it 'caches' responses from the remote server, and returns
subsequent requests for the same content directly.
 Proxy Server solves the problems of network congestion and
slow response time and provides control over network resources
without burdening end users or network administrators.
PURPOSES OF PROXY SERVER
Proxy servers have mainly two purposes:
 Improve performance :
Proxy servers can dramatically improve performance for
groups of users. This is because it saves the results of all requests for a
certain amount of time. Consider the case where both users X and
user Y access the World Wide Web through a proxy server. First user X
requests a certain Web page, which we'll call Page 1. Sometime later,
user Y requests the same page. Instead of forwarding the request to
the Web server where Page 1 resides, which can be a time-consuming
operation, the proxy server simply returns the Page 1 that it already
fetched for user X. Since the proxy server is often on the same

3. network as the user, this is a much faster operation. Real proxy
servers supports hundreds or thousands of users. The major online
services such as America Online, MSN and Yahoo, for example,
employ an array of proxy servers.
 Filter Requests:
Proxy servers can also be used to filter requests. For
example, a company might use a proxy server to prevent its
employees from accessing a specific set of Web sites.
WORKING OF PROXY SERVER
 The proxy server evaluates the request according to its filtering
rules. For example, it may filter traffic by IP address or protocol.
If the request is validated by the filter, the proxy provides the
resource by connecting to the relevant server and requesting
the service on behalf of the client.
 Proxy sites enable you to bypass your own Internet provider
and browse through the proxy web site. All that you have to
do is type the web site address you would like to visit in the
form they provide, and start browsing. Once you keep
browsing using that form, you are protected and your real IP
address is not being logged.
 Once you have configured your web browser as described,
your browser will load a CGI script each time it is restarted.
This script redefines the function that determines how to fetch
the URL that is being requested. If the URL matches a pattern
or a site that requires a proxy, it will connect to the proxy
server rather than going directly to the site.

4. Step 1: User starts browser, connects to proxy server to get the
Proxy
Automatic Configuration (PAC) file.
fetch request: proxy.ucla.edu/cgi/proxy
+-----+ +-----+
| U | | P |
| S | ==================>| X |
| R | | Y |
+-----+ +-----+
Step 2: Proxy server returns "proxy", which configures
browser to do proxying.
+-----+ +-----+
| U | "proxy" loaded | P |
| S |<================== | X |
| R | | Y |
+- +-----+ +-----+
Step 3: User requests URL, URL compared against function
retrieved from "proxy", connection route is determined.
Step 4a: Route for URL returned from function is "DIRECT"(no
proxy required). Browser retrieves URL directly. (*Note: At this
point, every URL returns "DIRECT" unless it is one that is know to
restrict access to ucla.edu*)
+-----+ +-----+
| U | fetch URL | S |
| S |<==================>| R |
| R | | V |
+-----+ +-----+
Step 4b1: Route for URL returned from function is "PROXY
xxxxx ” (proxy required). Browser contacts proxy server and
requests page.
+-----+ +-----+ +-----+
| U | request URL | P | | S |
| S | ==================>| X | | R |
| R | | Y | | V |
+-----+ +-----+ +-----+

5. Step 4b2: Proxy contacts server and requests page.
+-----+ +-----+ +-----+
| U | | P | request URL | S |
| S | | X | ==================>| R |
| R | | Y | | V |
+-----+ +-----+ +-----+
Step 4b3: Server sees request from ucla.edu domain (proxy
address ) and returns URL to proxy.
+-----+ +-----+ +-----+
| U | | P | return URL | S |
| S | | X |<================== | R |
| R | | Y | | V |
+-----+ +-----+ +-----+
Step 4b4: Proxy returns URL to User.
+-----+ +-----+ +-----+
| U | return URL | P | | S |
| S |<================== | X | | R |
| R | | Y | | V |
+-----+ +-----+ +-----+
TYPES OF PROXY SERVER
There are many different types of Proxy Servers out there. Depending
on the purpose you can get Proxy Servers to route any of these
common protocols, and many more ;
1) FTP Proxy Server:
Relays and caches FTP Traffic.
2) HTTP Proxy Server:

6. A one way request to retrieve Web Pages.
3) Socks Proxy Server:
A newer protocol to allow relaying of far more different types of data,
whether TCP or UDP.
4) NAT Proxy Server:
This one works a little different, it allows the redirection of all packets
without a Program having to support a Proxy Server.
5) SSL Proxy Server:
An extension was created to the HTTP Proxy Server which allows
relaying of TCP data similar to a Socks Proxy Server. This one done
mainly to allow encryption of Web Page
requests.
6) Caching proxy server:
A caching proxy server accelerates service requests by retrieving
content saved from a previous request made by the same client or
even other clients. Caching proxies keep local copies of frequently
requested resources, allowing large organizations to significantly
reduce their upstream bandwidth usage and cost, while significantly
increasing performance
7) Web proxy :
A proxy that focuses on World Wide Web traffic is called a "web
proxy". The most common use of a web proxy is to serve as a web
cache.

7. Furthermore, a Proxy Server can be split into another two Categories:
1) Anonymous:
An Anonymous Proxy Server blocks the remote Computer from
knowing the identity of the
Computer using the Proxy Server to make requests.
2) Transparent:
A Transparent Proxy Server tells the remote Computer the IP Address
of your Computer. This provides no privacy.
Functional Modules
1)Proxy User Interface :
This Module is responsible to control and manage the User Interface.
It will provide the user with an easy to use GUI, a window with menu.
The menu options should provide commands to perform the following
functions:
Start Proxy
Stop Proxy
Exit
Blocking URL

8. Blocking Client
Manage Log
Manage Cache
Modify Configuration
2) Proxy Server Listener :
The main function of the proxy starts here. This module will serve as a
Port listening to clients i.e. page requests from a web browser. It will
create a new connection for each request from the clients. One more
important feature of this module would to block clients which are
there in the blocked list given by the user.
3)Connection Manager
This module will contain the main functions of the Proxy Server. It
will read the request header from the client. It will parse the URL and
determine whether the URL is blocked or not. Else it will generate a
connection to the web server. Then it will read the reply header from
the web server. If there is no copy of the page in then cache then it
will download the page from Web Server else will check its last
modified date from the reply header and accordingly will read from
the cache or serve from the Web. Then it will also check the header
for caching allowed or not and accordingly will cache the page.
4) Cache Manager :
The Cache Manager is responsible for storing, deleting, clearing and
searching of web pages in the cache.

9. 5) Log Manager :
The Log Manager is responsible viewing, clearing and updating the
Log.
6) Configuration :
This module will enable the user to make his configuration settings. It
will work with the other modules to perform the desired
configurations such as caching (on/off), log (on/off), etc.
WEBSITES WHICH PROVIDES PROXY SERVERS
www.freeproxyserver.ca –
this proxy server provide a way to bypass school filter
www.proxyblind.org –
It is used to hide IP address of your computer .
www.publicproxyservers.com –
PublicProxyServers.com provides proxy lists solely based on
quality parameters of proxy servers
www.proxyway.com –
ProxyWay provides anonymous surfing and allows you to hide/
change IP address from the web sites you visit and your ISP.
You can easily configure different browsers/applications to work

10. through ProxyWay - you stay anonymous when you visit web sites,
download files, send emails, etc.
www.proxyserverprivacy.com/proxy-web-sites -
You can access blocked or restricted websites by using Yahoo
Babelfish or Google Translate language tools as a proxy server
www.topproxysites.com –
Top Proxy Sites and list server sorted out daily!
www.bestproxysites.com –
It provides you with a Free list of proxy websites for unfiltered web
www.daveproxy.co.uk-
If you require a proxy server that lets you anonymously surf the web
to the sites you want from our UK server
www.hideglobal.com –
HideGlobal.com - Free anonymous proxy sites, Free proxy server to
unblock websites myspace ,bebo, facebook - bypass web filter from
school and office .
DISADVANTAGE OF PROXY SERVER
1) It is possible for a computer to run as an open
proxy server without the computer's owner
knowing this. This can result from
misconfiguration of proxy software running on
the computer, or from infection
with malware (viruses, trojans or worms)
designed for this purpose.[2] If it is caused

11. by malware, the infected computer is known as
a zombie computer.
2) A feasible risk that a malicious proxy server
may record everything sent
3) the user may fall victim to a false sense of
security just because those details are out of
sight and mind
4) Does not filter content
5) Works only on single machine
6) GUI not controlled via K/B
7) There are hundreds of thousands of open
proxies online. This is rarely a matter of
misconfiguration, in most cases an open
proxy is unknown to the server owner.
Using an open proxy can be legally
dangerous: the current law in Germany,
for example, makes it illegal to access a
computer or network without the owner's
knowledge, even if the proxy is not
password-protected. There are no

12. reasons to run a clean open proxy for an
organisation, so any open proxy is
suspicious. The main sign of a legal open
proxy is the fact that it is not
anonymizing the connection
8) Running an open proxy is a high risk for
the server operator; providing an
anonymous proxy server can cause real
legal troubles to the owner. Such
services are frequently used to break into
foreign computer systems, child
pornography is usually consumed
through proxies, and illegal content is
likely to be spread through such proxies
9) Also, such a proxy can cause a high
bandwidth usage resulting in higher
latency to the subnetwork and violation
of bandwidth limits
10) A wrongly configured open proxy can
also allow access to a private
subnetwork or DMZ: this is a high
security concern for any company or

13. home network because computers that
usually are out of risk or firewalled can
be directly attacked.
11) The final disadvantage is that you may see
some issues with speed. Speed must be
weighed against the value of a cache, and how
much time it takes the request to traverse
several firewalls.