A web proxy server acts as an intermediary between clients and external servers on the internet. It protects clients by filtering traffic and limiting outside access. When a client requests a resource, the proxy server evaluates the request according to its rules before forwarding it to the external server. It then sends the response back to the client. This allows all clients connected to the proxy server to access the internet from behind the firewall with improved security and performance. The proxy server can also cache frequently requested resources to speed up access.

1. Web Proxy ServerWeb Proxy Server
BY:
Mohit Dhankhar
Hindu Institute of Management
Sonepat-131001

2. ProxyProxy
Proxy means a person authorized to act
on behalf of another. In communication,
a proxy is something that act as a server,
but when given request from client, act
itself as a client to the real server. For
example: An HTTP Proxy does not forward
every request sent through it.

3. 3
Proxy Server?Proxy Server?
Proxy server is a server that acts as an
intermediary for requests from clients seeking
resources from other servers. A client connects to
the proxy server, requesting some service, such
as a file, connection, web page, or other resource
available from a different server. The proxy
server evaluates the request according to its
filtering rules. For example, it may filter traffic
by IP address or protocol.

4. What is a Web Proxy Server?What is a Web Proxy Server?
It is a specialized HTTP Server.
Functions as a firewall.
– Protects client computers from Hackers by
limiting outside access to clients.
Allows all clients connected to Web Proxy
Server to access Internet from behind
“firewall.”
Client computer(s) are allowed access past
firewall with minimum effort and without
compromising security.

5. How Does A Web ProxyHow Does A Web Proxy
Server Work?Server Work?
Web Proxy Server listens for any request
from clients.
All requests are forwarded to remote
internet servers outside firewall.
Also listens for responses or request from
outside the firewall (external servers) and
sends to them to internal client computers.

6. Usually, all clients with a subnet use the
same proxy server.
This makes it possible for the proxy server
to cache documents that are requested by
one or more clients (repeatedly).
For clients using a web proxy server, it is as
if they are getting responses directly from a
remote server.

7. Types of proxyTypes of proxy
Forward proxies
Open proxies
Reverse proxies
Transport proxies
Anonymous proxies
Distorting proxies
7

8. TCP Connection TerminationTCP Connection Termination
 Both the outgoing and incoming TCP connections are terminated
 prevents a hacker from hijacking a stale connection on a service that is
being proxied
 ex . HTTP page request
User Proxy Server
request packet
request packet’
response packet’response packet
Connection left open until the
proxy closes it after receiving
response packet and sending it
back to user
Connection only left open until
server closes the connection after
sending the response packet

10. Proxy Server ExamplesProxy Server Examples
 A caching web proxy is a simple example of an
HTTP intermediary

11. Best PracticesBest Practices
 Use a Real Firewall
 Disable Routing
 Secure the Base Operating System
– harden the OS
 Disable External Access
 Disable unneeded Services

12. Security AdvantagesSecurity Advantages
 To provide security
 Hide internal clients from external network
 Hiding machine or another server from public
 To speed up access to resources
 Increase the performance
 Web proxies are commonly used to cache webpage from web server
 To protect your real identity on internet

13. An Ordinary Web Transaction ViaAn Ordinary Web Transaction Via
ServerServer
When the user enters:
– http://mycompany.com/information/ProxyDetails.html
 The browser converts it to:
– Get / information/ProxyDetails.html

14. Communicating Via Proxy ServerCommunicating Via Proxy Server
 The Proxy server acts as both a server system and a client
system.
 The proxy server uses the header fields passed to it by the
browser without modification when it connects to the
remote server.
 A complete proxy server should be able to communicate
all the Web protocols, the most important ones being
HTTP, FTP, Gopher, and WAIS.
 When a browser sends a request through a proxy server,
the browser always uses HTTP for the transactions with
the proxy server.

15. HTTP Browser Request to Remote HTTPHTTP Browser Request to Remote HTTP
TransactionTransaction
 An HTTP transaction via a proxy server

16. HTTP Browser Request to Remote FTPHTTP Browser Request to Remote FTP
TransactionTransaction
 An FTP transaction via a proxy server

17. Managing Cached DocumentsManaging Cached Documents
 Many documents available on the Internet are
“living” documents.
 Determining when documents should be updated
or deleted can be difficult task.
– Some documents can remain stable for a very long time
and then suddenly change.
– Other documents can change weekly or a daily basis.
 You need to decide carefully how often to refresh
or delete the documents held in cache.