A Canadian software company is helping Yemen’s Houthi rebels expand the country’s Internet censorship regime in the midst of a bloody civil war, according to a new report from the University of Toronto’s Citizen Lab.

The report says the Houthis have been using the Internet filtering software Netsweeper to impose new blocks on political content favorable to the deposed Saudi-backed government, as well as independent media outlets and any website bearing the Israeli “.isl” domain. When users in the country try to gain access to the newly blocked sites, they are redirected to fake “network error” pages, rather than pages that explicitly inform the user the page has been blocked.

Citizen Lab, which researches Internet censorship, said Netsweeper has provided filtering software to YemenNet, the country’s main Internet service provider, since approximately 2009. The new blocks took effect immediately after the takeover of Yemen’s capital, Sanaa, by Houthi forces in September 2014.

The report, based on 10 months of technical and in-country research, says that Netsweeper appears to be actively involved in the filtering of content in Yemen because it has been providing services to YemenNet since the Houthi takeover, and therefore “knows or has reason to know of the recent expansion of the filtering regime to include political content linked to the conflict and the Houthi takeover.”

“They can’t absolve themselves of what’s going on,” said Ron Deibert, director of the Citizen Lab. “By continuing to provide services to YemenNet in the middle of a civil war and humanitarian crisis, and while a rebel group targeted by U.N. sanctions is in control, Netsweeper is a party to the armed conflict acting on behalf of one of the belligerents.”

Al Jazeera was unable to reach Netsweeper despite repeated calls to its headquarters in Waterloo, Ontario. The company has also declined to respond to a Citizen Lab letter sent by email and fax on Oct. 9, requesting answers to a series of questions about Netsweeper’s human rights policies and due diligence.

The expanded censorship comes amid a bloody power struggle in Yemen between the Iran-linked Houthis, Saudi-backed forces loyal to deposed president Abd Rabbuh Mansur Hadi, and armed groups including Al-Qaeda and the Islamic State in Iraq and the Levant (ISIL). The conflict escalated sharply in March, when a Saudi-led coalition launched airstrikes aimed at Houthi targets. More than 1,500 civilians have been killed in the violence, the U.N. says.

Citizen Lab said restricting information can have serious consequences in a conflict. In May 2015, for example, disruptions in Yemen’s communications infrastructure, fuel supplies and electricity may have prevented “tens of thousands of civilians” from learning of and complying with a Saudi order to clear the cities of Marran and Sa’ada, which were subsequently bombed.

YemenNet's blocks targeted many independent news sites popular with Yemenis. The report did not specify whether those sites included information about the Saudi bombings. But, in general, Deibert said, “In denying citizens access to information in the midst of a humanitarian crisis, you’re putting people’s lives at risk. In an armed conflict situation, you want people getting more information for humanitarian reasons, not less.”

According to reports from the OpenNet Initiative, which includes Citizen Lab and two other institutions, Netsweeper won its contract in Yemen only after a U.S. company, Websense, pulled its services in 2009 amid criticism over facilitating censorship in the country. Websense then agreed to join the Global Network Initiative, a coalition of Internet companies that stands against censorship.

Netsweeper, a privately owned company that offers a line of Internet filtering services, does not disclose its contracts with foreign governments. In 2013, Citizen Lab reported that Netsweeper was also used by the Pakistani government to block sensitive religious topics and independent media, as well as by Somalia’s failed central government.

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