The US National Security Agency (NSA) was sued on 10 March by Wikimedia and other groups challenging one of its mass surveillance programs which they said violates Americans' privacy and makes individuals worldwide less likely to share sensitive information.

The lawsuit filed in federal court in Maryland, where the spy agency is based, said the NSA is violating US constitutional protections and the law by tapping into high-capacity cables, switches and routers that move Internet traffic through the United States.

"Our challenge asserts Fourth Amendment claims for the violation of Americans privacy. First Amendment claims for its effect on Americans' right to free expression and free inquiry. And it also asserts that the Challenge Spying Program goes beyond the authority given to the NSA when it passed a controversial spying law in 2008," said American Civil Liberties Union (ACLU) Attorney Patrick Toomey.

The NSA's upstream surveillance program captures communications with "non-US persons" in order to acquire foreign intelligence information. Toomey says NSA's indiscriminate copying and searching through Americans' international communications, imposes "a chilling effect" on Americans' basic freedoms.

"We have long operated in this country on a basic rule that the government does not search your home, your papers, and today your e-mails, when you've done nothing wrong," said Toomey. "And the flip side of that rule is that the government must go to court with individualized suspicion when it wants access to those materials."

The lawsuit follows the ACLU's failed attempt in 2013 to challenge the NSA's warrantless wiretapping program, which was shot down by the US Supreme Court on grounds that the plaintiffs could not prove that they had been spied on.

"What we have learned since the Stone disclosures began both from disclosures in the media and based on official acknowledgements from the government changes the equation entirely," said Toomey. "We now know that the spying that's occurring is far broader than we or the Supreme Court ever realized our previous challenge was ever litigated and the fact that the NSA is not simply surveilling the communication of its targets but it is surveilling the communications of essentially everyone to find information about those targets."

"We are asking the court to order an end to the NSA's dragnet surveillance of internet traffic," Wikipedia founder Jimmy Wales wrote in an opinion piece in the New York Times.

Major US technology companies suffering from the fallout of the NSA's mass surveillance programmes are also uniting to shore up their defences against government intrusion.