Network Defense Technology 1

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