HOUSTON -

A quick call on your phone may have an impact long after you hang up.

President Obama acknowledged Friday the government collects phone records in an effort to find terrorist plots. He said it's "watching out," as opposed to "listening in."

"What the intelligence community is doing is looking at phone numbers and durations of the call, not names, and they're not looking at content," Obama said.

There's Internet oversight too, Obama said, but it doesn't apply to U.S. citizens or people living in the United States, unless approved by a special court. He called the programs classified, not secret, because every member of Congress has been briefed.

"Within the past few years, this program was used to stop a terrorist attack in the United States, we know that," said Obama.

The programs were first reported by the Guardian and the Washington Post this week, though some details in the reports have since been questioned.

Collecting all of the data about all Americans' phone calls can't possibly be useful for link-based investigations.

Many civil rights and privacy groups are concerned about the monitoring scope--the ACLU called it "Beyond Orwellian."

Obama said you can't have 100 percent security and also have 100-percent privacy and no inconvenience, but critics fear surveillance tips the balance too far the wrong way.