(Reuters/Kacper Pempel/Files)

Since 2013, Americans have gained immense insight about how the government conducts digital spying programs, largely thanks to the revelations made by former security contractor Edward Snowden. But a new report shows it's really hard to keep track of all the ways the United States is snooping on its own people.

After Snowden revealed the National Security Agency was collecting data en masse about American e-mails, the government said it had ended that particular program in 2011.

But it turns out that didn't really stop the NSA from being able to suck data about Americans' e-mails: Instead, the government was able to replace the key functions of that program by relying on legal methods designed to collect information about foreigners, according to a NSA Inspector General report obtained by the New York Times via a Freedom of Information Act suit. And because those methods focused on overseas collection, or collection aimed at non-U.S. citizens, they largely had less oversight than the now-defunct domestic e-mail records program.

"This is yet another trick move in the never-ending shell game that the NSA is playing with the American people, and apparently with the secret court whose oversight it is trying to evade," said Kevin Bankston, the director of New America's Open Technology Institute. "New rule: if the NSA claims that a particular surveillance program has ended, or that a particular type of surveillance has halted 'under this program,' assume that it is still going on in another program."

There is a reason for all the secrecy: The government argues it has a vested interest in keeping capabilities secret so that terrorists and other targets aren't able to figure out how to evade surveillance. That's one of the reasons some intelligence officials were quick to blame Snowden in the wake of the recent Paris attacks, arguing his revelations may have given terrorists a road map for how evade detection.

"[I]in the past several years because of a number of unauthorized disclosures and a lot of handwringing over the government’s role in the effort to try to uncover these terrorists, there have been some policy and legal and other actions that are taken that make our ability collectively internationally to find these terrorists much more challenging," CIA Director John Brennan said Monday at a Washington conference.

But no evidence has yet emerged that the attacks were coordinated using tools that protected communications through encryption, a security tool Snowden often recommends to everyday users looking to ensure their digital privacy. In fact, the information available so far suggests that the attackers sent an unencrypted text to coordinate the launch of the attack, and several of them had been known to Belgian investigators.

The lack of transparency and public awareness of how Americans' data was being collected is also one of the reasons Snowden said he was compelled to come forward with information about government spying.

“My sole motive is to inform the public as to that which is done in their name and that which is done against them,” he wrote in a note that accompanied the first document he leaked to The Washington Post.

But big disclosures such as Snowden's come along rarely. And now we're seeing that reporting on these programs is like a sort of like playing whack-a-mole: Even if one program appears to have ended, others spring up in their place -- and the general public often doesn't learn about them until years after they've taken effect.