Definition 1: A proxy
server is a computer that
offers a computer network service to allow clients to make indirect network
connections to other network services. A client connects to the proxy server,
then requests a connection, file, or other resource available on a different
server.
Definition 2: In computer networks, a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers.
Definition 3: A proxy server is a dedicated computer or a software system running on a computer that acts as an intermediary between an endpoint device, such as a computer, and another server from which a user or client is requesting a service. The proxy server may exist in the same machine as a firewall server or it may be on a separate server, which forwards requests through the firewall.
Main Proxy Functions
1) Caching
2) Firewall
3) Filtering
4) Logging
Advantages of Proxy
Server
1) Terminates the TCP connection before relaying to target host (in
and out)
2) Hide internal clients from external network
3) Blocking of dangerous URLs
4) Filter dangerous content
5) Check consistency of retrieved content
6) Eliminate need for transport layer routing between networks
7) Single point of access, control and logging
Disadvantages
Disadvantages
- All data came through this server, if this server was compromised it’s mean that all user use the server have possibility information / data theft.
- If this proxy were located at ISP(Internet Service Provider), Campuss, School and there’s a bad employee or staff inside, it’s also possible data theft happen. And sometimes this bad guy will know you more than yourself
Purposes
of Proxy Server: Why Proxy Server
1) Faster
access to the requested resources.
2) Enables
high security.
3) Undesired
sites are blocked.
4) Contents
are scanned for spyware or malware before receiving.
5) Outbound
content is also scanned.
6) Increases
performance.
7) Requests
can be filtered.
Types of Proxy Server
1) Anonymous Proxy
- An anonymous proxy server also known as web proxy, generally attempts to anonymize web surfing by hiding
the original IP address of the end user. This type of proxy server are
typically difficult to track, and provides reasonable anonymity for most users.
This
type of proxy server identifies itself as a proxy server, but does not make the
original IP address available. This type of proxy server is detectable, but
provides reasonable anonymity for most users.
2) Distorting Proxy
- This type of proxy server identifies itself as a proxy server, but make
an incorrect original IP address available through the http headers.
3) High Anonymity Proxy
- This type of proxy server does not identify itself as a proxy server and
does not make available the original IP address. High anonymity proxies, only
include the REMOTE_ADDR header with the IP address of the proxy server, making
it appear that the proxy server is the client.
4) Intercepting Proxy
- An intercepting proxy, also known as a transparent proxy, combines a
proxy server with a gateway. Connections made by client browsers through the
gateway are redirected through the proxy without client-side configuration.
These types of proxies are commonly detectable by examining the HTTP headers on
the server side.
5) Reverse proxy
- A reverse proxy is another common form of a proxy server and is
generally used to pass requests from the Internet, through a firewall to
isolated, private networks. It is used to prevent Internet clients from having
direct, unmonitored access to sensitive data residing on content servers on an
isolated network, or intranet. If caching is enabled, a reverse proxy can also
lessen network traffic by serving cached information rather than passing all
requests to actual content servers.
6) Transparent Proxy
- A transparent proxy is a server that satisfies the definition of a
proxy, but does not enforce any local policies. It means that it does not add,
delete or modify attributes or modify information within messages it forwards.
These are generally used for their ability to cache websites and do not
effectively provide any anonymity to those who use them. However, the use of a
transparent proxy will get you around simple IP bans. Further, your web browser
does not require special configuration and the cache is transparent to the
end-user. This is also known as transparent forward proxy.
This type of proxy
server identifies itself as a proxy server and also makes the original IP
address available through the http headers. These are generally used for their
ability to cache websites and do not effectively provide any anonymity to those
who use them. However, the use of a transparent proxy will get you around
simple IP bans. They are transparent in the terms that your IP address is
exposed, not transparent in the terms that you do not know that you are using
it (your system is not specifically configured to use it.)
How proxy
servers work:
When a proxy
server receives a request for an Internet resource (such as a Web page), it
looks in its local cache of previously pages.
If it finds
the page, it returns it to the user without needing to forward the request to
the Internet.
If the page
is not in the cache, the proxy server, acting as a client on behalf of the
user, uses one of its own IP
addresses to request the page
from the server out on the Internet.
When the
page is returned, the proxy server relates it to the original request and
forwards it on to the user.
Use of Proxy servers are used for both legal and illegal purposes. In the
enterprise, a proxy server is used to facilitate security, administrative
control or caching services, among other purposes. In a
personal computing context, proxy servers are used to enable user privacy and anonymous surfing. Proxy servers can
also be used for the opposite purpose: To monitor traffic and undermine user
privacy.
To the user, the proxy server is invisible; all Internet requests and returned responses appear to be
directly with the addressed Internet server. (The proxy is not actually
invisible; its IP address has to be specified as a configuration option to the browser or other
protocol program.)
Tunneling proxy.
A
proxy server that passes requests and responses unmodified is usually called a gateway or
sometimes a tunneling proxy.
A
forward proxy is an Internet-facing proxy used to
retrieve from a wide range of sources (in most cases anywhere on the Internet).
A reverse proxy is
usually an internal-facing proxy used as a front-end to control and protect
access to a server on a private network. A reverse proxy commonly also performs
tasks such as load-balancing,
authentication, decryption or caching.
Reverse proxies are used:
·
To enable indirect access when a
website disallows direct connections as a security measure.
·
To allow for load balancing between
severs.
·
To stream internal content to
Internet users.
·
To disable access to a site, for
example when an ISP or government wishes to block a
website.
An open proxy
is
a forwarding proxy server that is accessible by any Internet user.
An anonymous open
proxy allows
users to conceal their IP address while browsing the Web or using
other Internet services.
Examples
of Proxy Servers:
1)
CCProxy
Proxy Server Software
2)
WinGate
Proxy Server Software
3)
Squid
Proxy Server Software
4)
Nginx
Proxy Server Software
