In this post i will try to explain how firewalls work. And a couple of simple ways to go around them.
Generally a site can be blocked in your by Three types for firewall blocks.
The first type actually blocks a fixed set of sites.This one is easy to bypass.All you got to do is find a proxy site on the net and surf.Or you can setup your own proxy by getting a hosting account.
The second type actually blocks sites based on the content it has. Things are pretty hard in such a case since even when you go through the proxy, the content still gets filtered.
The third one is kind of hybrid of the first two it has list of sites which keep updating and also blocks site based on the content.
Here i will be telling some of the methods to bypass a simple firewall.
Use of Anonymizers (Proxy servers)
Proxy servers can not only be used to make your surfing anonymous but also to access blocked sites.However you may have to be abreast with the proxy sites as your administrator would be adding them to blocked as he comes to know about it. one good way is to subscribing to groups like http://groups.google.com/group/proxy-group which will keep giving new proxy sites to use every week,or simply do a google search for the latest list as this is a very dynamic area
Another worth mentioning sites would be google transalate by using the URL
http://www.google.com/translate?langpair=en|en&u=www.blockedsite.com or any other transalation tool for the matter like altavista,now yahoos babel fish.
How does it work ?
Proxy servers are computers outside your company's firewalls accessed via the internet. They have their own IP address and are able to be controlled via your computer. Your computer connects to a proxy server and the proxy server is the computer that makes the connection with the blocked web site. The proxy server then shows you the contents of the page. You can view the web site and even interact with the web site through the proxy server.As for your firewall it would seem your only talking with another site which is not banned.
Basically what we are doing here is we are connecting to a third party site which in turn routes your request to the required server. This method however may not be v secure .
Now some intelligent once might ask , instead of making some 3rd party computer as my proxy server can i make my home pc my proxy server ? ... You sure can n that will be the best way to do it for many reasons , 1. You wont leave any trace of what you have done on the office pc
2. You are connecting to your comp and hence more secure .
This can be achived by doing remote desktop or using softwares like http://www.logmein.com
or if you are using linux u can just run nomachine nx and connect to your home computer over SSH .
If your gmail and other mail serives have been blocked in your office and you want to keep a check on your you may simple forward those mails to your office account by using a filter of important email address or use rss feed.Rss feeds like google reader and friendfeed are yet to be blocked atleast in mine :D
I will be explaining about making your home pc a proxy server and mail forwarding in one of the coming post .
If your PC is directly connecting to the internet and firewall is of type 1 u may first want to try the below
IP Address
This is the first thing you should try if find a site is blocked.Find the ip address of the side and put in the address bar.If your firewall is very basic(type1) this might work.
How to find the ip-addess ? simple ! go to command prompt and type in "nslookup www.sitename.com" for ex:nslookup www.yahoo.com as shown below
else you can also use websites like this or this
Using Google Cache
Instead of going directly to the web site using the URL, go to the home page of Google and search for the web site or web site page you want to access. Once Google shows you the possible choices that are indexed, choose to retrieve the blocked web page using Google's cache copy of the page. Since these pages are copied into Google's database, in most cases the site will not be blocked.
Happy Browsing :)let me know how you people bypass the firewall
