How countries and corporate bodies block Internet
China’s most famous blogger, author of best-sellers and race car driver, Han Han, took a jab at his government last April after he was named one of the 100 most influential people by Time magazine. In his blog twocold he wrote, “Other Chinese nominees include sensitive word, sensitive word and sensitive word.” His post, referring to China’s web censors’ habit of blocking even commonplace names from web searches and blog sites, struck a chord with his readers. Within days, more than 20,000 commented on his post, most echoing Han’s exasperation with the Chinese censorship of the Internet.
China has one of the most advanced web monitoring and blocking systems. The system can be likened to a check at the airport. Every piece of luggage, coming in or going out, is put through a scanner. If any one of them contains weapons or narcotics, the scanner detects it immediately and the articles are impounded. Web filters work in a similar way. They scrutinise and block websites which could range from websites on free speech and democracy to ones on pornography, depending on the country using the system.
Internet sites can be blocked at different levels.
Censoring begins at home
The most basic form of censorship is the one parents employ at homes to prevent their children from browsing adult content. This can be done by altering a file called the host, which is a text document. The host file is like a contact list in your mobile phone where each name has a corresponding coordinate. It guides domain names to their respective Internet protocol (IP) addresses. Every device (computer or mobile) connected to the Internet has a unique IP address. Tweaking the host file ensures a user will not be able to access the desired website even when he has typed the correct domain name. Names of websites to be blocked can be added to a list in this file and directed to the loopback IP 127.0.0.1, a reserved IP address used when a programme needs to access a network service running on the same computer. When the user types the name of a website, the loopback IP will bring it back to the user’s machine, showing an error on the screen.
When blocking has to be done on a larger scale, like at the corporate or national level, all computers are routed through an intermediary device called a proxy server. These servers work as a front for a group of computers that connect to other network servers. Filters in these servers scan content as well as uniform resource locators (URLs). URL blocking is simple. The proxy server has a database of URLs called a black list, that it will block. It also contains a white list of URLs that can be browsed. Proxy servers’ URL databases are updated through web-based subscription services just like an anti-virus software.
|HOW PROXY SERVER WORKS
Proxy servers have a database of URLs divided into black and white lists. All sites in the black list are blocked. Proxy servers block content in a similar way
|VPN & ANONYMISERS CAN CIRCUMVENT CENSORS
Virtual Private Network (VPN) creates a virtual tunnel through which data is sent in encrypted form to a remote server/computer which decodes it. Anonymiser websites act as proxy servers, shielding client’s identity and information
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