Watching you: how much government surveillance should Americans accept to keep the nation safe from more terrorist attacks?

• Author: Smith, Patricia
• Position: Cover story

Since the deadly Sept. 11, 2001, attacks, Americans have grown accustomed to increased security and government scrutiny in their daily lives: body scanners and shoe searches at airports, video surveillance cameras on many buildings and city streets, and more intrusive questions at border crossings.

But this spring's news that the U.S. government has been secretly collecting Americans' telephone records and tracking foreigners overseas on sites like Yahoo and Facebook has raised questions about how much privacy is worth sacrificing to keep the nation safe.

"You can't have 100 percent security and also then have 100 percent privacy and zero inconvenience," President Barack Obama said after the phone and Web tracking programs were disclosed in June. "We're going to have to make some choices as a society."

Edward Snowden, a 30-year-old former contractor for the National Security Agency (N.S.A.), leaked details of the surveillance programs to the media, risking a long prison sentence for disclosing top-secret material.

"The public needs to decide whether these programs and policies are right or wrong," he said.

Under the phone surveillance program, begun in 2006 under President George W. Bush, the N.S.A. collects phone company records showing numbers called within the U.S. and call durations; it does not listen in on calls. The Internet surveillance program, called Prism, started the following year; it involves eavesdropping on e-mails and online chats of foreigners overseas. The government obtained court orders to force companies like Google, Yahoo, and Facebook to turn over online communications from their databases.

President Obama calls the programs "modest encroachments on privacy" and says they are "worth us doing" to protect the country. The programs, he says, were authorized by Congress and are regularly reviewed by federal courts.

Information gathered under Prism has helped foil about 50 terrorist plots, according to N.S.A. director Keith Alexander. In 2009, an intercepted e-mail led authorities to arrest an

A Privacy Violation?

But some see such surveillance as a serious infringement on Americans' privacy. The idea of a fight to privacy comes from the Constitution's Fourth Amendment, which protects against "unreasonable searches and seizures" (see box). It means, for instance, that the police need a court-issued warrant to search your home.

The American Civil Liberties Union (A.C.L.U.) has sued the Obama administration over its...