How Internet contents are blocked?

One of my friend use to visit my website ( in his office once in a while to see the updates and new postings, few of my colleagues were also enjoying it. But day before yesterday when he tried to open my website, a message was thrown that  “access to this site is denied” by his organization.  I was surprised, under what category or under which rule my page was blocked?  However it was very clear that his administrator has specifically submitted this site in the filter list to block the access. He must be thinking that my friend was wasting his ‘precious’ time in reading this website only..ha..ha..ha!  


Are we so immature that Organizations/Corporate/Government has to intervene to get maximum from us by restricting access to sports, news, stocks, mails, blogs and other perfectly normal websites?  Personally I don’t think so. Some illegal sites and contents that threaten the security, peace and happiness of the country should obviously be blocked or censored from the Internet. Also, in corporate world, if website content compromises with their legal & compliance structure or can be a threat for data security, then they should be blocked.  But, normal websites like Gmail, Yahoo, social sites, entertainment, sports, news etc should be available for users. Visiting these sites is just like taking a break to refresh ourselves. The person who want to waste time, you can’t stop him…he will waste time in gossips, cigarette break, tea break and many more ways that I don’t know.  

Let me tell you one thing that most of the Western governments provide their citizens with unblocked Internet access. Are they less productive than us?

There are various reasons for blocking contents on Internet like: Security, Legal, Economic interests, Moral, Bandwidth, Waste of time and resource etc.

Most common stuffs which are getting blocked are: Social networking sites, Video & Audio streaming websites, Sports websites, Job search websites, Blogs, Torrents, Instant messengers, News websites , Emails (Yahoo, Gmails etc).

Let’s find out how these Internet contents are blocked:

There are various techniques & tools used by the organizations, companies and colleges to block the contents on the internet. Following are the techniques majorly used for blocking the contents.

  1. URL (Uniform resource Locator) blocking: A uniform resource locator, abbreviated URL, also known as web address, is a specific character string that constitutes a reference to a resource (website). In most web browsers, the URL of a web page is displayed on top inside an address bar. An example of a typical URL would be “”. In this technique, the entire URL address is scanned for any blocked domain or keywords. When user try to access such URL and in case any blocked domain or keyword is found then he gets an access denied message.
  2. DNS (Domain Name System) Filtering:  When you type a domain name (like in your browser, your browser convert it into its respective IP (like ) address through a DNS (Domain Name Server) lookup query. If browser didn’t know the IP address of the website then will not able to connect to it. Using this technique organizations or companies block the DNS lookups for some domain names. If a browser cannot perform DNS lookup for a particular domain, then it would not be able to access it.
  3. IP (Internet Protocol ) address blocking: In this technique IP address is blocked by the network administrator.
  4. Packet filtering: In this method, the communication between the user and a website is monitored for certain predefined keywords and the moment any blocked keyword(s) is detected, the connection is reset or disconnected.  
  5. Portal censorship and Filtered search: Major portals, including search engines, may exclude web sites that they would ordinarily include. This renders a site invisible to people who do not know where to find it. When a major portal does this, it has a similar effect as censorship. Sometimes this exclusion is done to satisfy a legal or other requirement, other times it is purely at the discretion of the portal. For example and remove Neo-Nazi and other listings in compliance with German and French law.
  6. Proxy Filtering : A proxy server is a server (a computer system or an application) that acts as an intermediary for requests from user seeking resources from other servers. Whenever a user sends a request for a webpage to a proxy server, the proxy server forwards that request to the relevant server on the Internet and then send back the response to the user. In this method, the proxy server will monitor all the websites that user is trying to access and can be configured to block or redirect the user if he try to access any blocked website.
  7. Network disconnection: A technically simpler method of Internet censorship is to completely cut off all routers, either by software or by hardware (turning off machines, pulling out cables).  
  8. Port Blocking: A port serves as an interface between the computer and other computers or peripheral devices. This is a door through which data enters or leaves your computer. There are two types of ports :  Hardware and Software (virtual).  Some web applications open certain local ports (virtual) on your computer or connect to a port on the remote computer. Such port is required by the application for its basic function and communication on the Internet.  To block such type of web applications network administrators simply block the use of such ports. Applications like Skype can be blocked by this technique.
  9. Commercial Software and Applications: Many software and applications which are multifunctional provided by the Internet security companies are primarily marketed to businesses and individuals seeking to protect themselves and their employees and families, they are also used by governments to block what they consider sensitive content.

There are many techniques (using IP address, Translation, Format changer, aliases, URL shortening, proxy servers etc) which can unblock such type of blocking / filtering but we should avoid using such methods and should respect our organizations policies.  But in the meantime, you should also fight for your right to see the content which is legal and normal. Don’t be a culprit by breaking the rules but strive for betterment of the rules!


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6 Responses to How Internet contents are blocked?

  1. Prashant Sharma says:

    good one alok but its better if you aalso reveal some technique to open blocked sites. I am fed up of these blockings in my organisation

  2. Shruti says:

    I want to highlight that blockings are not very helpful in safety of organisations network. This mainly becuase of they don’t trust their employees. I am from network security and understand the need and application. Good point to raise Alok.

  3. Steafen says:

    I think this going to be one of the best article on internet on blocking. Information with some reasoning shows that you have depth man…u gotta right spike.

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