The Postal Service uses a program to examine mail similar to the NSA surveillance program, a new report reveals.

The US Postal Service photographed approximately 160 billion envelopes, packages and postcards last year, The New York Times reported.

Postal Service computers take pictures of the exterior of every single piece of mail. The surveillance is known as the Mail Isolation Control and Tracking program. It is similar to surveillance of emails and phone calls by the National Security Agency.

While letters and packages cannot opened without a warrant, the tracking program collects images of the outsides of every package mailed in the U.S.

The mail covers program has been used for over a century but the postal service "spying" program broadly expanded it.

"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, a former FBI agent for 34 years, said.

It is not known how long the government saves the images. They may have lead to warrants in cases including the ricin-tainted letters sent to Obama and Mayor Bloomberg.

The program may have helped the FBI arrest Shannon Richardson, of Texas, for allegedly mailing ricin-tainted letters to President Obama and New York City Mayor Bloomberg.

The mail original mail cover program lets enforcement officials ask postal workers to record information from the outsides of mail before it's delivered to an individual. These requests are granted for 30 days and can be extended for up to 120 days.

Computer security expert Bruce Schneier said that the program can track "names, addresses, return addresses and postmark locations, which gives the government a pretty good map of your contacts, even if they aren't reading the contents."

Law enforcement officials say that these programs are essential to national security, but many feel it is an encroachment on the privacy of citizens.