How to block users from accessing certain websites

Following is one of many ways to block users from accessing certain websites.

Background: When a user tries to launch a open a website from the browser, Windows by default tries to resolve the website name to its IP address from the local DNS cache first. If this fails, it will query the hosts file and if no entry for the website is there, it will finally contact the DNS server for name resolution. Provided that the user does not have the website IP address cached, the hosts file can be used to do the block. Incase the user does have the website IP address cached, a simple restart to the DNS service will clear the cache.

Solution: Open the file "C:\Windows\System32\drivers\etc\hosts" and add an entry as below:

127.0.0.1 domainname.com

(domainname.com being the website you want to block. Save the hosts file outside the etc folder and then move it there, replacing the older version, as Windows won't let you save the file there directly. Also make sure there's no extension like .txt at the end of the file name)

This way whenever a user tries to go to anything.domainname.com, their browser redirects them to 127.0.0.1 which is the local host. Or maybe you can redirect them to an HTML page stating the reason why that page is blocked from within your organization.