A team of Canadian researchers have uncovered an unusual new example of “upstream filtering,” where online content in one country is blocked in another country due to filtering that happens in transit.

Researchers at the Citizen Lab at the Munk School of Global Affairs at the University of Toronto, revealed that some Oman Internet users using the Omantel ISP are also being subjected to Indian content restrictions because of traffic flowing through India.

“It goes to show what you can find when you begin to probe beneath the surface of the Internet, and what you see when you have governments start to mess with the openness of the Internet,” Ron Deibert, Citizen Lab's director, told Ars on Thursday. “In this case you have a perverse situation where citizens in one country are subject to filtering in another country.”

While there have been numerous examples of specific countries blocking foreign or domestic content that they find objectionable, as it runs afoul of their own laws or regulations, it’s rare for one country to accidentally block sites due to peering agreements and traffic flows.

In this case, Indian ISP Bharti Airtel and Omantel have peering agreements, and partnered with other companies to build the Europe India Gateway, a 15,000-kilometer fibre optic cable that connects 13 countries via the Suez Canal in Egypt.

Citizen Lab conducted numerous tests in late June 2012 both remotely via a proxy, and also in collaboration with Omani Internet users, but also found that the blocks may not be consistently applied at all times.

Entertainment, news sites affected

“The practice of upstream filtering raises a number of questions, including jurisdictional issues and the lack of recourse to users in Oman,” Citizen Lab states in its report.

“The application of filters in India restricts Internet users in Oman from accessing content, potentially even content produced in Oman itself, as a result of actions taken for domestic purposes within India. Users in Oman did not consent to this blocking, are left with little recourse for challenging these actions, and have limited means of accessing this content, which may or may not be in violation of Omani regulations. Combined with the significant filtering implemented by Omantel itself, this essentially puts Internet users in Oman behind multiple layers of national-level filtering.”

Primarily, the sites affected included Indian and Pakistani entertainment sites, political blogs, file-sharing websites, and even IndyBay, a San Francisco-based online news site.

Not surprisingly, many Internet watchers lament this odd state of affairs online.

“Decisions made in one country about acceptable online content often affect users in other countries,” wrote Jillian York, the director for international freedom of expression at the Electronic Frontier Foundation, in an e-mail sent to Ars on Thursday. “This can occur through upstream filtering such as in this scenario or through application of a bill like SOPA, where the US government would have been enabled to make decisions about foreign content."

Similar examples in Central Asia

Oman has its own national filtering system, written in Arabic and English, which announces that it blocks content that is “contrary to the laws of the Sultanate.” Omantel users seeing the Indian block are shown an English-only message, which states: “This website/URL has been blocked until further notice either pursuant to Court orders or on the Directions issued by the Department of Telecommunications.”

The Department of Telecommunications is the name of India’s telco regulations agency. But beyond the name coincidence, running a traceroute from Oman or an Oman proxy, shows that the traffic to a US-based site runs through India.

India tends to filter security and Internet tools-related content, according to previous research done by the Open Network Initiative (ONI), while Oman’s tend to be more along the lines of blocking pornographic material, gay and lesbian content, and circumvention tool-related sites.

The ONI is a grouping of similar institutions that also includes the SecDev group and the Berkman Center for Internet and Society at Harvard University. In its extensive research on Internet filtering around the world, ONI has found similar examples in the past. Most notably there was a case in Kyrgyzstan, which had some sites blocked by a state ISP from Kazakhstan while selling its service to Kyrgyz Telecom.

“Similar behavior was observed in Uzbekistan in 2004, where content filtering on one Uzbek ISP closely matched that seen in China, a finding supplemented by evidence that this ISP was purchasing connectivity service from China Telecom,” the Citizen Lab added in the report.

Of course, any Omantel user or any other Internet user with a VPN or other circumvention tool would easily get around such blocks—a service that a New Zealand ISP advertised earlier this year with the express purpose of getting around Hulu and Netflix's geoblocking.