In statements on that and reports about collecting phone data, Clapper also called out those behind the apparent leaks -- saying it "will have an impact on the behavior of our adversaries and make it more difficult for us to understand their intentions."
Speaking specifically about collecting personal phone records, privacy advocates called the practice perilous and claimed it gives authorities access to information of many Americans who aren't terrorists. In fact, they might not necessarily be Verizon customers, and similar orders might also apply to other telecommunications companies.
"There is no indication that this order to Verizon was unique or novel," said the Electronic Frontier Foundation, which fights to protect privacy.
"It is very likely that business records orders like this exist for every major American telecommunication company, meaning that, if you make calls in the United States, the NSA has those records. And this has been going on for at least seven years, and probably longer."
Al Gore: 'Secret blanket surveillance obscenely outrageous'
This group is hardly alone.
The American Civil Liberties Union called it "beyond Orwellian (in allowing) basic democratic rights (to be) surrendered in secret to the demands of unaccountable intelligence agencies."
The Center for Constitutional Rights blasted it as "the broadest surveillance order to ever had been issued: It requires no level of suspicion."
Many in President Barack Obama's own party spoke forcefully against it as well.
Three Democratic representatives -- John Conyers of Michigan, Jerrold Nadler of New York and Robert Scott of Virginia -- said the program is "highly problematic and reveals serious flaws in the scope and application of the" Patriot Act.
"(The revelations) confirm our fears -- that the law would be distorted to allow for ongoing, indiscriminate collection of data," they wrote.
Sen. Mark Udall, who serves on the Senate Intelligence Committee, described the program as "the kind of government overreach I've said Americans would find shocking."
One of them: former Vice President Al Gore.
"Is it just me, or is secret blanket surveillance obscenely outrageous?" the 2000 Democratic presidential nominee wrote on Twitter.
Senator says ending program would be 'catastrophic'
Opinions were also strong on the other side of the debate.
"Terrorists will come after us if they can, and the only thing that we have to deter this is good intelligence to understand that a plot has been hatched and to get there before they get to us," said Feinstein.
Her intelligence committee's ranking Republican, Sen. Saxby Chambliss of Georgia, concurred in stating the program has let authorities gather "significant information on bad guys and only on bad guys over the years."
Former FBI Assistant Director Tom Fuentes, a CNN contributor, said that if a phone number comes up that's linked to someone suspicious, they can go back and get information tied to that number.
"It's not that someone or some group of analysts can sit there and monitor 50 million phone calls going through the computers," Fuentes explained on CNN's "Starting Point." "But it would create the ability to go back and see if you could connect phone calls."
Rep. Lindsey Graham said that, as a Verizon customer, "it doesn't bother me one bit for the National Security Administration to have my phone number." The South Carolina Republican said he's confident the government won't monitor his and other innocent Americans phone calls just because their "number pops up on some terrorist's phone."
"The consequences of taking these tools away from the American people through their government would be catastrophic," he said.