Turkey's Internet crackdown has expanded from Twitter to the Domain Name System (DNS), according to Google.
"We have received several credible reports and confirmed with our own research that Google's Domain Name System (DNS) service has been intercepted by most Turkish ISPs (Internet Service Providers)," Google software engineer Steven Carstensen said in a Saturday blog post.
A DNS server converts alphabetic website names into numeric IP addresses, "in the same way that you might look up a phone number in a phone book," Carstensen said.
"But imagine if someone had changed out your phone book with another, which looks pretty much the same as before, except that the listings for a few people showed the wrong phone number," he said. "That's essentially what's happened: Turkish ISPs have set up servers that masquerade as Google's DNS service."
After Turkey blocked Twitter, many citizens directed their devices to the Google public DNS IP addresses, 188.8.131.52 and 184.108.40.206 or Level 3 at 220.127.116.11 and 18.104.22.168. The numbers were spray painted on buildings and political posters to spread the word.
Turkish Prime Minister Recep Tayyip Erdogan blocked the micro-blogging service on March 20 after the company reportedly ignored court orders to remove "illegal" links. A week later, he took similar action against YouTube after an audio recording featuring top government and military officials discussing Syrian security was uploaded to the site.
Internet monitoring firm Renesys confirmed Google's report and said that Level 3 DNS servers were also hijacked.
"Now local users of these global DNS services are surreptitiously redirected to alternate providers within TurkTelekom," the company said in a blog post that called the move "ominous."
"Now when Turkish users seemingly ask a Google DNS server for YouTube's address, they get the IP address of a Turkish government site (22.214.171.124), explaining the ban," the company said.
"The real damage may come in the years ahead if businesses decide to invest less in Turkey because of the uncertainty around the free flow of information," Renesys suggested. "While social media sites are not necessarily central to many business operations, if Twitter and YouTube can be blocked today, what about Gmail or Dropbox tomorrow?"
The ban came in advance of local elections in which Erdogan emerged victorious,The New York Times reported. A presidential election is also scheduled for the summer, while parliamentary elections are set for next year.