How does DNS Website Blocking Work ?

The TCP/IP protocol in Windows contains a file called “hosts“  that contains the mapping of the website to a particular IP address. Whatever DNS address you may use in your router or modem or your TCP/IP properties in Network Connection, they will be overridden by the IP mapping done in this “host” file. So by simply mapping any website to a dummy IP we can block the particular website from loading in the browser.

How to block a website using DNS

1. Open the folder “C:\Windows\System32\Drivers\etc“
2. In that folder you can find a file by the name “hosts“, right click on the file and open it with notepad or any other text editor.
   

   IP Mapping

3. As in the above show image, the last lines represents the IP mapping, so add the IP address “127.0.0.1″ followed by the website that you want to block.
4. The address “127.0.0.1″ is the localhost address, (you can specify any other dummy IP in that place if you want to )
5. Save the File
6. Restart your Browser and now you can find that the website you have added will fail to load.

How to check if a website is blocked by DNS

There are many ways by which you can find whether a website has been blocked to you or not. Following are some of the methods by which you can find out.

Direct Host File Lookup

Nothing can be much easier than this method, to check the website is blocked by DNS or not, just open the host file specified in the folder “C:\Windows\System32\Drivers\etc” , However administrators are smart enough, they would have already restricted you from viewing the System Files, In those cases you got to try the following methods.

Down for Everyone Or Just Me

This is one of the mostly viewed website to detect if a website is not available just to you or to everyone. Enter the website that you want to check and there you can find out if the site has been blocked. However this method cannot precisely determine if its blocked because of the DNS. There may be several ways by which ca website can be blocked ,DNS is one such way.

IP Lookup

Since DNS methods maps the website to some dummy address, whenever you ping the website, it in return pings the IP that has been mapped to it. Open Command Prompt and type  “ping“  followed by the website name. This will show the IP that been associated with it. Comparing it to the original IP you can find if the site has been blocked by DNS or not.

Open a Blocked website

If you cannot get a chance to edit the IP mapping table, you can still open the blocked website using proxy websites. HideMyAss is one such proxy website viewer, that can help you in this case.

HideMyAss