A web proxy server functions as a firewall by limiting outside access to client computers and protecting them from hackers. It allows clients connected to the proxy server to access the internet from behind the firewall with minimal effort and without compromising security. The proxy server listens for requests from clients and forwards them to remote internet servers, and also listens for responses to send back to clients. This allows the proxy server to cache frequently requested documents and control internet access at the protocol level.

1. WEB PROXY
SERVER
A Presentation on Proxy Server
Vikas Reddy Merugu

2. 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.

3. HOW DOES IT WORKS ?
• 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.
• 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).

4. CONTINUE…
• For clients using a web proxy server, it is as if
they are getting responses directly from a
remote server.
• Clients without a Domain Name Service can
still access the Web
• All that is needed is the proxy server’s IP
address.
• Most Web Proxy Servers are implemented on
a per-access method
basis.
• It can allow or deny internet requests
according to the protocol
used.
• For Example: A proxy server can allow
calls to FTP while but deny
calls to HTTP servers.

5. HOW DO BROWSERS ACCESS
INTERNET ?
• In some cases, certain browsers cannot
access the Web because they are behind
a firewall.
• In these cases, the web proxy server can
retrieve any desired files for them.

6. CONTROLLING ACCESS TO
INTERNET
• Web proxy server makes it possible to filter
client “transactions” at the protocol level.
• Controls access to services for individual
methods, hosts, as well
as domains.
• For Example, web proxy servers allows
administrators to:
• Decide which requests to grant permission
to and which ones to turn down.
• Specify the URL(s) masks of locations that
you don’t want the proxy server to serve.
• Specify which protocols clients can use the
services based on their IP address.

7. COMMUNICATING THROUGH
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.

8. HOW PROXY ACCESS CONTROL
WORKS ?
• Scenario: an off-site (or off-campus) user connects to the
Internet via an ISP and wants to connect to an IP-
restricted resource:
- user Y from outside internal network requests access to
internal resource- proxy server prompts user Y for
validation.
- user Y is validated (proxy server masks user Y's IP-
address)
- resource.com assumes user Y is an institutional
computer

9. Thank you for your kind
attention