On Wednesday, someone at Chile's Domain Name System (DNS) registry, the Internet Protocol (IP) address lookup system, said a local Internet service provider had noticed strange behavior and asked his counterparts in other parts of the world about it on an industry e-mail list.
Specifically, one of the main DNS root servers, called the I Root Server and operated in Sweden, was directing visitors trying to go to those sites instead to servers in China. This effectively sent people behind the Great Firewall of China, a strictly controlled network of servers and routers the People's Republic of China uses to filter the Internet and block its citizens from accessing content deemed politically sensitive.
Representatives from Twitter and Facebook did not respond to calls and e-mails seeking comment on Thursday night.
A spokesman for Google, which owns YouTube, declined to comment, saying "this appears to be a specific ISP level issue." He said it was not related to Google's English-language corporate site appearing in Chinese, Danish, and other languages on Wednesday, which the company attributed to a bug.
For more of this story, read Web traffic redirected to China in mystery mix-up on CNET News.