Senator Mark Udall, above, and Senator Ron Wyden have warned Americans that their government is spying on them [EPA]

The rise of government surveillance is a troublesome legacy of the September 11 attacks. Today, video cameras are visible everywhere in public places, recording people’s every move. But what about spying that can’t be spotted?

Ten years after 9/11, new questions are being raised about what the US government is secretly doing on the internet and through satellites, using the Patriot Act and other national security law as justification.

Two American senators with access to top-secret intelligence raised the alarm in May, suggesting that the invasion of law-abiding Americans’ privacy was being carried out clandestinely - and that people would be shocked if they knew the extent.

“I want to deliver a warning this afternoon,” Senator Ron Wyden said on May 26 during a Senate debate. “When the American people find out how their government has secretly interpreted the Patriot Act, they will be stunned and they will be angry.” 

Exactly what activities US agencies are carrying out remains unclear. Senator Wyden and Senator Mark Udall - also on the Senate Select Committee on Intelligence - have been unable to elaborate on their accusations because of official secrecy law.

However, observers surmise that ordinary people may be caught up in an electronic dragnet searching for terrorists. Civil liberties advocates suggest that intelligence and law-enforcement agencies may be reading and cataloguing people’s e-mails in databases, as well as tracking their mobile phone locations.

US Justice Department public affairs officer Dean Boyd dismissed the senators’ allegations. “It’s quite unfortunate that your facts are so incorrect,” Boyd told Al Jazeera English when asked about Wyden and Udall’s comments.

Boyd highlighted one provision of the Patriot Act in his response, Section 215. “Contrary to various claims in recent months and years, Section 215 is not a secret law, nor has it been implemented under secret legal opinions by the Justice Department,” he said.

But the American Civil Liberties Union hasn’t been satisfied with that answer. The group has launched an extensive campaign to find out exactly how portions of the Patriot Act have been interpreted, and whether e-mails were being swept up and mobile phones tracked without probable cause.

Michael German is a 16-year FBI veteran of counterterrorism operations who quit the bureau and later joined the ACLU. He told Al Jazeera English: “It’s clear the government is broadly collecting information regarding innocent Americans. It appears officials no longer need individualised suspicion, and a person’s good conduct does not protect them from scrutiny.”

The evolution of national security law

Congress overwhelmingly passed the original Patriot Act in October 2001 after the 9/11 attacks, arguing that its broad powers were necessary to protect the country from terrorism. Civil liberties advocates have long questioned whether some aspects of the law threatened people’s privacy.

As debate took place in May on a vote to extend the Patriot Act for another four years, Senators Wyden and Udall warned that the executive branch had come up with a secret legal theory about what personal information it could collect, which didn’t dovetail with a plain reading of the text.

Wyden and Udall continued to press for transparency after the Patriot Act extension was passed in late May. They sent a letter to the Director of National Intelligence, James R Clapper, who oversees 16 spy agencies, including the National Security Agency and Central Intelligence Agency. The senators asked whether legal safeguards were in place to protect the electronic communications of law-abiding Americans under another security law, the Foreign Intelligence Service Act (FISA).

"It is a matter of public record that there have been incidents in which intelligence agencies have failed to comply with the FISA Amendments Act, and that certain types of compliance violations have continued to recur," Wyden and Udall wrote. "We believe it is particularly important to gain an understanding of how many Americans may have had their communications reviewed as a result of these violations."

Kathleen Turner, from the Office of the Director of National Intelligence, told the senators that it was not “reasonably possible to identify the number of people located in the United States whose communications may have been reviewed".

Wyden wasn’t happy with the answer. “I understand that it may be difficult to come up with an exact count … but I believe that Congress at least needs to obtain an estimate of this number, so that people can understand the actual impact of the FISA Amendments Act on the privacy of law-abiding Americans,” he said. 

Turner assured that the privacy rights of ordinary Americans were being protected. “We believe that we have put in place a robust compliance and oversight regime,” she told the senators.

Top NSA lawyer admits Americans’ phones may be tracked

Another topic of concern raised by the senators is geo-location data - information generated by electronic devices such as cell phones, wirelessi-equipped laptops, and GPS navigation units - that can be used to determine where people are.

Wyden and Udall highlighted “conflicting judicial rulings on the legality of the government surreptitiously tracking an individual’s movements using a mobile electronic device”.

Are government agencies tracking mobile phones and other digital devices of law-abiding Americans?

At a Senate hearing on July 26, Sen. Wyden went head-to-head with the top lawyer at the National Security Agency, Matthew Olsen. “Do government agencies have the authority to use cell-site data to track the location of Americans inside the United States for intelligence purposes?” Wyden asked. 

Olsen replied: “I think there are certain circumstances where that authority may exist”.

The ACLU announced in August that it filed hundreds of requests with law enforcement agencies throughout the country to uncover when, why and how they are using cell phone location data to track Americans.

Part of the problem, said German, is that legal protections haven’t kept up with the rapid advance of technology. “We have a perfect storm where technology has outpaced how the law protects individual privacy. The law hasn’t been updated, even though much of our lives are spent in an electronic world.”

If US agencies are spying on law-abiding Americans’ e-mails and phones, the next question is, why? German said that it is “official culture” to collect as much data on people as possible. The attitude is “while this person may not being doing something wrong today, what if they do something bad a year from now?”.

But not only does bulk data collection undermine democracy, it also fails to help root out terrorists, the former covert operations specialist said. Gathering vast amounts of information on the innocent only serves to blanket the bad guys, said German.

“It’s a foolish approach that affects innocent people, and it doesn’t actually help the government. The real threats get lost in the noise.”

One person with an insider’s view is Thomas Drake, a former top official at the National Security Agency from 2001 through 2008. Disturbed by what he describes as "malfeasance, fraud and illegalities" at the United States' largest spy agency, he blew the whistle and was later prosecuted by both the Bush and Obama administrations.

Drake called out the government in an August 26 Washington Post opinion piece entitled, "Why are we subverting the Constitution in the name of security?"

"Shortly after Sept. 11, I heard more than rumblings about secret electronic eavesdropping and data mining against Americans ... Before the war on terrorism, our country recognised the importance of free speech and privacy. If we sacrifice these basic liberties, according to the false dichotomy that such is required for security, then we transform ourselves from an oasis of freedom into a police state," Drake wrote.

As for the dogged Sen. Wyden, his fight to expose secret surveillance law has not finished. “It’s my view that we have to keep (intelligence) operations and methods secret, but we’ve got to also have public awareness of the laws on the books.”