In addition to the email and phone metadata the U.S. government is tracking, the feds also have an eye on your regular old snail mail, which is actually a "treasure trove of information," according to a former FBI agent who used to work with the Mail Isolation Control and Tracking program, as it's called. One would think that snail mail, a relic from a former century, wouldn't provide that much insight into our lives — isn't it all bills and unwamted brochures by now? But, it's just about as useful, it not more so, than digital collection. "Looking at just the outside of letters and other mail, I can see who you bank with, who you communicate with — all kinds of useful information that gives investigators leads that they can then follow up on with a subpoena," James J. Wedick, the FBI agent, told The New York Times's Ron Nixon.

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That's pretty much what the NSA can find through digital tracking, as explained here, but the mail surveillance program is even worse from a privacy advocates standpoint because there is zero oversight. "You just fill out a form," Wedick explains. The U.S. Postal Service grants or denies the request without any judicial overview — there's not even a secret court involved. And it's all okay, say courts, because people shouldn't expect privacy for the outside of their mail. Which: sure, anyone can look at the outside of a given envelope. But, is that the same thing as someone rifling through our mail every single day? Apparently.

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The government has used that argument to justify digital surveillance, notes Nixon. "Officials in both the George W. Bush and Obama administrations, in fact, have used the mail-cover court rulings to justify the N.S.A.’s surveillance programs, saying the electronic monitoring amounts to the same thing as a mail cover," he writes. Congress hasn't even talked about the physical mail tracking program since 1976, even with "sporadic" reports of abuse, like opening letters to and from the Soviet Union. The whole thing sounds like a disturbing look at how the current digital surveillance program will look in 40 years: After debate, the program continues, people forget about it and then it's a weird precedent for more tracking.

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Also eerily similar to the current NSA PRISM program, we have no idea how many requests the USPS gets with regards to terrorism:

The criminal activity requests average 15,000 to 20,000 per year, said law enforcement officials who spoke on the condition of anonymity because they are prohibited by law from discussing the requests. The number of requests for antiterrorism mail covers has not been made public

That sounds a lot like the non-figures we didn't get from Facebook, Google, and all the other participants who can't say how often the government requests terrorism related intel.

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There is one glimmer of hope, however: At least the snail mail tracking program has led to some successful arrests in Medicare fraud and drug trafficking. It's hard to say the same for PRISM right now.