What is a proxy server ?

A proxy server is a server (a computer system or an application program) that acts as an intermediary for requests from  users called 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.

A proxy server serves following functions:

• To keep the identity of machines as  anonymous.
• To speed up access using caching.  
• To apply access policy to network services or content, e.g. to block undesired sites.
• To log / audit usage, i.e. to provide company employee Internet usage reporting.
• To bypass security/ parental controls.
• Check outbound content by scanning the data.

A proxy server that passes requests and replies unmodified is usually called a gateway . 
A proxy server can be placed in the user's local computer or at various points between the user and the destination servers on the Internet.

Types of proxy servers:

1.Content Filtering web proxy: 
This web proxy server provides administrative control over the content that may be relayed through the proxy. It is commonly used in both commercial and non-commercial organizations (especially schools) to ensure that Internet usage conforms to decided criteria.

2. Anonymizing proxy server:
An anonymous proxy server (sometimes called a web proxy) generally attempts to anonymize web surfing.   One of the more common variations is the open proxy. Because they are typically difficult to track, open proxies are especially useful to those seeking online anonymity .Some users are merely interested in anonymity for added security, hiding their identities from potentially malicious websites for instance, or on principle. . The server receives requests from the anonymizing proxy server, and thus does not receive information about the end user's address. However, the requests are not anonymous to the anonymizing proxy server, and so a degree of trust is present between that server and the user.


3.Tunneling proxy server:
A tunneling proxy server is a method of defeating blocking policies implemented using proxy servers. Most tunneling proxy servers are also proxy servers, of varying degrees of sophistication, which effectively implement "bypass policies".
A tunneling proxy server is a web-based page that takes a site that is blocked and "tunnels" it, allowing the user to view blocked pages.
                                                                                                    (SRC:Wikipedia)


List of some free proxy sites: 

1. http://www.hidemyass.com
2. http://www.anonymizer.com
3. http://www.wujie.net
4. http://www.ultrareach.net
5. http://surfshield.net 
6. http://proksi.us 
7. http://anonymouse.ws/anonwww.html
8. http://www.browser-x.com
9. http://www.spysurfing.com
10. http://www.xerohour.org/hideme
11. http://www.proxyz.be
12. http://www.sc0rian.com/prox
13. https://www.proxify.us
14. http://kproxy.com/index.jsp
15. http://www.brawl-hall.com/pages/proxy.php
16. http://www.proxify.net
17. http://proxy.computersteroids.com/index0.php
18. http://www.unipeak.com
19. http://flyproxy.com
20. http://alienproxy.com

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