Tensions were high as the National Security Agency’s Gen. Keith Alexander took the stage here in front of a packed room of security industry professionals and hackers of all stripes.

The general at the forefront of the surveillance scandal currently enveloping the NSA walked up to the podium in the conference center at Caesar’s Palace amid audience murmurings that he was going to avoid the issue.

Instead, it was the focus of his keynote speech.

“How do we protect our civil liberties and privacy?” he asked the 3,200 people filling the room and the 1,500 people in an overflow space. “This is one of the biggest issues we face today.”

He also promised the attendees that he would take their questions, a longtime tradition at Black Hat and its sister conference, DefCon. “I will answer every question to the fullest extent possible. We don’t want to jeopardize our defense,” he said.

It was a far cry from when Alexander kicked off DefCon 20 with a keynote speech last year. There’s a lot of crossover between Black Hat and DefCon attendees, but the general, who last year was dressed in jeans and a tucked-in T-shirt, spoke on Wednesday in his official uniform. This would be a more serious presentation.

Over the ensuing 45 minutes or so, Alexander described in broad terms how Section 702 of the FISA Amendment Act and Section 215 of the Patriot Act affect governmental intelligence gathering in the U.S.

His described the pre-9/11 world as a place where the intelligence community was at times unable to “connect the dots” in order to stop terrorist attacks. Post-9/11, he said, problems continued, but the situation improved. He cited phone surveillance that led to the arrest of Najibullah Zazi, who was involved in the plot to bomb the New York subway in 2010, as one example of successful surveillance.

About a half-hour into Alexander’s presentation, some in the audience had enough.

“Freedom!” shouted a man who Forbes identified as 30-year-old security consultant Jon McCoy.

“Exactly,” Alexander said. “We stand for freedom.”

“Bullshit!” retorted McCoy.

Alexander kept his cool and replied, “Not bad,” to mild applause from the crowd. People didn’t necessarily buy everything that Alexander was selling, but they weren’t entirely comfortable with the heckling either.

“But I think what you’re saying is that in these cases, what’s the distinction, where’s the discussion, and what tools do we have to stop this?” Alexander said.

McCoy yelled back, “No, I’m saying I don’t trust you!”

Moments later, another audience member chimed in. “You lied to Congress. Why would people believe you’re not lying to us right now?”

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Hackers to NSA chief: Read the Constitution | Security & Privacy – CNET News.