
In  a rare public accounting of its mass surveillance program, the U.S.  Postal Service reported that it approved nearly 50,000 requests last  year from law-enforcement agencies and its own internal inspection unit  to secretly monitor the mail of ordinary Americans for use in criminal  and national-security investigations.
 
 The number of requests, contained in a little-noticed 2014 audit  of the surveillance program by the Postal Service’s inspector general,  shows that the surveillance program is more extensive than previously  disclosed and that oversight protecting Americans from potential abuses  is lax.
 
 The audit, along with interviews and documents obtained by The New  York Times under the Freedom of Information Act, offers one of the  first detailed looks at the scope of the program, which has played an  important role in the nation’s vast surveillance effort since the  terrorist attack of Sept. 11, 2001.
 
 The audit found that in many cases the Postal Service approved  requests to monitor mail without adequately describing the reason or  having proper written authorization.
 
 In addition to raising privacy concerns, the audit questioned the  efficiency and accuracy of the Postal Service in handling the requests.  Many were not processed in time, the audit said, and computer errors  assigned the same tracking number to different requests.
 
 “Insufficient controls could hinder the Postal Inspection  Service’s ability to conduct effective investigations, lead to public  concerns over privacy of mail and harm the Postal Service’s brand,” the  audit concluded.
 
 The audit was posted in May without public announcement on the  website of the Postal Service inspector general and got almost no  attention.
 
 The surveillance program, officially called Mail Covers, is more  than a century old but is still considered a powerful investigative  tool. At the request of state or federal law-enforcement agencies or the  Postal Inspection Service, postal workers record names, return  addresses and any other information from the outside of letters and  packages before they are delivered to a person’s home.
 
 Law-enforcement officials say this deceptively old-fashioned  method of collecting data provides a wealth of information about the  businesses and associates of their targets, and can lead to bank and  property records and even accomplices. (Opening the mail requires a  warrant.)
 
 Interviews and court records also show that the surveillance  program was used by a county attorney and sheriff to investigate a  political opponent in Arizona — the county attorney was later disbarred  in part because of the investigation — and to monitor privileged  communications between lawyers and their clients, a practice not allowed  under postal regulations.
 
 Theodore Simon, president of the National Association of Criminal  Defense Lawyers, said he was troubled by the potential for the Postal  Service to snoop uncontrolled into private lives.
 
 “It appears that there has been widespread disregard of the few protections that were supposed to be in place,” he said.
 
 In information provided to the Times earlier this year under the  Freedom of Information Act, the Postal Service said that from 2001  through 2012, local, state and federal law-enforcement agencies made  more than 100,000 requests to monitor the mail of Americans. That would  amount to an average of some 8,000 requests a year — far fewer than the  nearly 50,000 requests in 2013 that the Postal Service reported in the  audit.
 
 The Postal Service also uses a program called Mail Imaging, in  which its computers photograph the exterior of every piece of paper mail  sent in the U.S. The program’s primary purpose is to process the mail,  but in some cases it is also used as a surveillance system that allows  law-enforcement agencies to request stored images of mail sent to and  received by people they are investigating.
 
 Another system, the Mail Isolation Control and Tracking Program,  was created after anthrax attacks killed five people, including two  postal workers, in late 2001, and is used to track or investigate  packages or letters suspected of containing biohazards such as anthrax  or ricin.
 
 The program was first made public in 2013 in the course of an  investigation into ricin-laced letters mailed to President Barack Obama  and former Mayor Michael R. Bloomberg of New York City by an actress,  Shannon Guess Richardson.
 
 Defense lawyers say the secrecy concerning the surveillance makes  it difficult to track abuses in the program because most people are not  aware they are being monitored. But there have been a few cases in which  the program appears to have been abused by law enforcement.
 
 In Arizona in 2011, Mary Rose Wilcox, a Maricopa County  supervisor, discovered that her mail was being monitored by the county’s  sheriff, Joe Arpaio. She had been a frequent critic of Arpaio,  objecting to what she considered the targeting of Hispanics in his  immigration sweeps.
 
 The Postal Service had granted an earlier request from Arpaio and  Andrew Thomas, who was then the county attorney, to track Wilcox’s mail.
 
 She sued the county, was awarded nearly $1 million in a settlement  in 2011 and received the money this June when the U.S. 9th Circuit  Court of Appeals upheld the ruling.