Turkish Prime Minister Recep Tayyip Erdogan has moved to ban Twitter in his country following a series of social media leaks that have fomented a corruption scandal and challenged his long-running authority. Erdogan has been in power for 11 years. International outcry against his action was swift and loud, and Turkey’s leading press organization even took legal action this week against the ban.
Former Secretary of State Hillary Clinton herself took to Twitter this weekend, saying that “The freedom to speak out and to connect is a fundamental right. The people of Turkey deserve that right restored.”
Turkey first and foremost started filtering using the domain name system. DNS takes care of translating website names into IP addresses so computers can connect to the correct site. Most networks run one or more local domain name servers to perform this task. One of the ways an entity can attempt to filter a domain is to corrupt how these name servers process their requests, effectively hijacking the domain from the perspective of the local users relying on that name server.
“In the case of Turkey, the government does not necessarily run all of the name servers within the country,” explained Chris Brenton, director of security at Dyn, in a comment to Infosecurity. “They do however have legal jurisdiction over the ISPs operating within the country’s borders. So Turkey’s first attempt at blocking Twitter was to hijack the twitter.com domain on name servers running within their borders.”
The problem for the government, however, is that circumventing DNS filters is simple: citizens can just avoid using the name servers that are returning corrupted information. Many individuals within Turkey almost immediately started using Google’s public DNS service, altering the DNS settings on their devices to allow them to use the service.
From there, Turkey’s next response, carried out over the weekend, was somewhat expected, Brenton said. “When the Turkish government learned that people were using alternate name servers, they began implementing an IP block against those servers. Filtering by IP address is the big stick used to block Internet communications.”
The problem here though is simple scale. “While both DNS and IP filter can be successfully implemented at the corporate level, they start to break down as the network and user base grows exponentially in size,” he said. “Attempting to implement filtering at a country level is incredibly problematic.”
That’s not to say it hasn’t been done – China’s famous “Great Firewall” is an example of a country enabling this countrywide. But it does take significant resources to do it effectively.
“There have been a huge number of stories talking about the attempts of the Turkish government to ban all access to Twitter,” Benton said. “Yet, while many of these stories talk about the political implications or how the Turkish people can get around the ban, there is no good description of why the ban is a technically futile effort.”