WASHINGTON — Under fire for the worst privacy debacle in his company’s history, Facebook CEO Mark Zuckerberg batted away often-aggressive questioning Tuesday from lawmakers who accused him of failing to protect the personal information of millions of Americans from Russians intent on upsetting the U.S. election.

During some five hours of Senate questioning, Zuckerberg apologized several times for Facebook failures, disclosed that his company was “working with” special counsel Robert Mueller in the federal probe of Russian election interference and said it was working hard to change its own operations after the harvesting of users’ private data by a data-mining company affiliated with Donald Trump’s campaign.

Hawaii’s two senators — Brian Schatz and Mazie Hirono — were among the dozens of senators who questioned the tech mogul.

Hirono’s questioning of Zuckerberg veered in a different direction than her Senate colleagues. Her primary concern was whether Facebook would cooperate with the Trump’s administration’s push for “extreme vetting” of immigrants.

AP/Andrew Harnik

She cited an Immigration and Customs Enforcement proposal that seeks to use publicly available information — including data from social media sites, such as Twitter, Facebook and Instagram — to determine if someone would be a “positively contributing member of society” or make “contributions to the national interest.”

She said that proposal also seeks to develop ways for ICE to predetermine whether someone intends to commit a criminal or terrorist act after coming into the country.

“Does Facebook plan to cooperate with this extreme vetting initiative and help the Trump administration target people for deportation or other ICE enforcement?” Hirono asked.

“We would not proactively do that,” Zuckerberg said.

He added that Facebook does cooperate with law enforcement when there’s an imminent threat of harm and if the company receives a valid legal subpoena or request for information or data.

Zuckerberg noted that the company will push back, however, if the subpoena is overly broad.

Schatz took a different approach in his questioning of Zuckerberg.

He pointed out that while Facebook says that users “own” their own personal data and can do with it what they want, that doesn’t appear to be the case because Facebook is the one monetizing it.

“It doesn’t seem to me that we own our own data, otherwise we would be getting a cut,” Schatz said.

Zuckerberg replied that it’s true that users have control over their own data and can do with it what they will. But he also noted that by using the platform it provides the company with a “license” to use it.

The senator turned to an idea that would require Facebook to act as an “information fiduciary,” similar to a doctor, lawyer or accountant, that is entrusted with sensitive information and could get in trouble if that information were to be released publicly.

“Are you open to the idea of an information fiduciary enshrined in statute?” Schatz, who is considering legislation on the issue, asked.

Zuckerberg didn’t answer directly. But he did say the idea was “interesting” and “worth consideration.”

Before the hearing started, hundreds of people — including some wearing “#Delete Facebook T-shirts — waited in line trying to catch a glimpse of Zuckerberg. But the Facebook CEO entered the hearing room via a private elevator.

The hearing itself was moved to accommodate the 44 senators and the large audience.

Inside the hearing, many senators took full advantage of the platform, using their time to express their frustrations with Zuckerberg and his company, which boasts 2.2 billion users, and to pontificate.

At the heart of the Senate inquiry is concern about Russian meddling in U.S. elections and the improper harvesting of the personal data of 87 million users by Cambridge Analytica, a British firm used by President Trump’s campaign in 2016.

But it became clear early on that the hearing was much bigger than that.

“Would you be comfortable sharing with us the name of the hotel you stayed in last night?” Illinois Sen. Dick Durbin asked Zuckerberg.

“Um,” Zuckerberg paused, with couple of slight chuckles. “Uh, no.”

The response brought laughter to the room. But Durbin wasn’t done.

“If you messaged anybody this week would you share with us the names of the people you’ve messaged?” he asked before the audience could settle back to silence.

“Senator, no, I would probably not choose to do that publicly here,” Zuckerberg said as the smile began to fade from his lips.

“I think that may be what this is all about,” Durbin pointed out. “Your right to privacy and the limits to the rights to privacy. And how much you give away in modern America in the name of quote ‘Connecting People Around the World.’”

Zuckerberg will appear at a House hearing Wednesday.

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