Facebook CEO Mark Zuckerberg made his highly-anticipated appearance before Congress on Tuesday and apologized for his company's shortcomings and failure to protect users' information in the wake of the Cambridge Analytica scandal and Russian interference in the 2016 election.

"We didn't take a broad enough view of our responsibility, and that was a big mistake, and it was my mistake, and I'm sorry," Zuckerberg told lawmakers. But many of the senators weren't buying the 33-year-old billionaire's apology.

"We've seen the apology tours before," said Sen. Richard Blumenthal, D-Connecticut.

"After more than a decade of promises to do better, how is today's apology different?" said Sen. John Thune, R-South Dakota.

Next up, Zuckerberg will meet face his second public grilling before a House committee.

The latest:

• Facebook stock jumps higher during testimony
• How to check if your Facebook data was shared
• Zuckerberg: Facebook is working with special counsel Robert Mueller
• CNET: 5 notable themes from Mark Zuckerberg's opening testimony

Follow updates from Zuckerberg's testimony below:

Round 1 comes to a close

The first day of questioning has come to a close. Next up, Zuckerberg will field questions from the House of Representatives on Tuesday. We'll be back with the live blog, live stream and analysis.

Zuckerberg's notes

7:27 p.m.: Associated Press photographer Andrew Harni got a clear shot of Zuckerberg's notes as he left the table during a break Tuesday. Some notable entries include how he should defend Facebook. "[If attacked: Respectfully, I reject that. Not who we are.]"

There's even a section titled: "Resign?" that seems to dodge the question entirely.

"Founded Facebook. My decisions. I made mistakes. Big challenge, but we've solved problems before, going to solve this one," it reads. "Already taking action."

​Kogan gave Facebook data to firms besides Cambridge Analytica

6:56 p.m.: Responding to a question from Sen. Tammy Baldwin, D-Wisconsin, Zuckerberg said app developer Aleksandr Kogan gave the illicit user data to other firms besides Cambridge Analytica, including Eunoia.

"He sold it to other firms. There was one called 'Eunoia' and a couple of others as well," Zuckerberg said, promising to provide the companies names to her after the hearing.

"Your user agreement sucks"

6:44 p.m.: Sen. John Kennedy, R-Louisiana, told Zuckerberg straight up that his user agreement sucks.

"Here's what everybody has been trying to tell you today, and I say this gently: Your user agreement sucks," Kennedy said, as Zuckerberg held back a smile.

"The purpose of that user agreement is to cover Facebook's rear end. It's not to inform your users about their rights," Kennedy said.

"You can spot me 75 IQ points. If I can figure it out, you can figure it out. The purpose of that user agreement is to cover Facebook's rear end, it's not to inform your users about their rights. You know that and I know that. I'm going to suggest that you go home and rewrite it."

Zuckerberg: I don't remember decision not to inform users of data misuse

6:30 p.m.: Sen. Kamala Harris, D-California, listed questions Zuckerberg seemed to dodge Tuesday afternoon.

"During the course of this hearing, you've been asked several critical questions for which you don't have answers. Those questions have included: whether Facebook can track activity after a user logs off of Facebook, whether Facebook can track you across devices even when you aren't logged into Facebook. Who is Facebook's biggest competition, whether Facebook may store up to 96 categories of users information."

She then asked Zuckerberg if he was a part of the decision not to tell users their data was collected by Cambridge Analytica.

"I don't remember a conversation like that," Zuckerberg said. "I'm not sure whether there was a conversation about that but I can tell you the thought process at the time."

​"Is Facebook too powerful?"

6:14 p.m.: Sen. Dan Sullivan, R-Alaska, asked Zuckerberg if his company has become too powerful.

"Are you too powerful? Do you think you are too powerful?" Sullivan asked.

Zuckerberg didn't directly answer the question, but said, "We need to have a conversation about the right regulation."

Sullivan said regulation "can cement the dominant power" and said one of his biggest concerns is that Facebook is becoming "so dominant that we won't be able to have the next Facebook."

Does Facebook listen to users' voices, and record phone call data?

5:58 p.m.: Senator Gary Peters asked if Facebook listened to users and collected the audio data. Zuckerberg replied a definitive "no" and suggested that was a "conspiracy theory."

5:51 p.m.: Senator Dean Heller asked Zuckerberg where he drew the line on what kind of data Facebook would sell to advertisers. Zuckerberg was quick to correct the Nevada senator saying Facebook doesn't sell data.

Heller pressed on other privacy questions asking if Facebook recorded phone calls. Zuckerberg said he didn't believe they ever collected the content of phone calls.

During the exchange with Senator Heller, Zuckerberg acknowledged the 87 million people whose data were shared are victims.

"It happened on our watch," Zuckerberg acknowledged.

​Facebook "would not proactively" work with ICE

5:57 p.m.: Sen. Mazie Hirono, D-Hawaii, asked Zuckerberg if Facebook plans to aide President Trump's "extreme vetting" initiative and help Immigration and Customs Enforcement (ICE) target people for deportation.

"If you were asked to cooperate with ICE so that they could determine if somebody is going to commit a crime, for example, or become fruitful members of our society would you cooperate?" Hirono asked.

"We would not proactively do that," Zuckerberg said. "We cooperate with law enforcement in two cases: if we become aware of an imminent threat of harm, then we will proactively reach out to law enforcement, as we believe is our responsibility to do."

He said the other instance is when law enforcement sends Facebook "a valid legal subpoena or request for data, in those cases, if the request is overly broad or we believe it isn't a legal request, we are going to push back aggressively."

​Who’s sitting behind Zuckerberg?

5:44 p.m.: Joel Kaplan, Facebook's vice president of global public policy, is sitting directly behind Zuckerberg at the hearing. Kaplan previously served as President George W. Bush's deputy chief of staff for policy from 2006 to 2009.

Myriah Jordan, Facebook's public policy director, is seated to the left of Zuckerberg. Jordan previously worked as an aide for Bush in his chief of staff's office, according to her LinkedIn profile.

​Senators introduce bill of rights

5:21 p.m.: Sens. Edward J. Markey, D-Mass., and Richard Blumenthal, D-Conn., unveiled a "privacy bill of rights" as Zuckerberg before Zuckerberg arrived to testify Tuesday. The bill would require the Federal Trade Commission (FTC) to establish protections for customers of companies like Facebook and Google.

During questioning, Markey asked if Zuckerberg would support a legislation in the U.S. that would require companies to get people's permission before their information is used for any reason.

"I think that that's the right principal," Zuckerberg said, adding that he looks forward to meeting with the senator to speak on the details of the bill.

​Zuckerberg: Facebook doesn't hire consultants to get people hooked

5:14 p.m.: Sen. Ben Sasse, R-Nebraska, asked Zuckerberg about social media addiction: "Do you hire consultants to tell you how to tap into dopamine feedback loops to keep people addicted?"

"No, senator. That's not how we talk about this or set up our product teams," Zuckerberg said.

Sasse then asked if Zuckerberg was aware of social media companies hiring such consultants.

"Not sitting here today," Zuckerberg said.

Did Palantir work with Cambridge Analytica?

4:41 p.m.: Responding to Sen. Maria Cantwell about reports that technology company Palantir also scrapped Facebook data, Zuckerberg seemed caught off guard but said he wasn't aware of any incidents in which it did. Palantir was co-founded by entrepreneur Peter Thiel, who serves on Facebook's board of directors.

Zuckerberg also said that he didn't know if Facebook employees had worked directly with Cambridge Analytica.Jennifer Grygiel, a social media expert and assistant communications professor at Syracuse University, said she was surprised at Zuckerberg's reaction to the line of questioning."It's another social media data analytics company that does alot of listening.

They work with police departments around the world, Thiel had founded the company and he is also on the board of Facebook," Grygiel said. "It was widely reported that somebody from Palantir had gone and helped Cambridge Analytica in the design of their app so it was surprising that he punted that one."

The New York Times reported, citing documents, that a Palantir employee worked closely with Cambridge Analytica to build their model for psychological profiling and suggested the data scientists create an mobile app to access the information of Facebook users' friends.

Ted Cruz asks Zuckerberg if Facebook is biased against conservatives

4:30 p.m.: Sen. Ted Cruz asked Zuckerberg if his company is biased against conservatives.

"Does Facebook consider itself to be a neutral public forum?" Cruz asked.

Zuckerberg said despite being located in the left-leaning Silicon Valley, the company doesn't have "any bias" in the work that they do."

"We consider ourselves to be a platform for all ideas," Zuckerberg responded.

Durbin makes it personal

4:15 p.m.: Sen. Dick Durbin tried to simplify the privacy issue facing Zuckerberg and Facebook by making it personal.

"Would you be comfortable sharing with us the name of the hotel you stayed in last night?" Durbin asked.

"Uh... no," Zuckerberg said.

Durbin then asked if Zuckerberg would share the names of everyone Zuckerberg messaged this week. "Senator, no, I would not choose to do that publicly here," he responded.

Durbin said "maybe what this is all about: Your right to privacy."

"The limits of your right to privacy. And how much you give away in modern America, in the name of, quote, connecting people around the world," he added.

Zuckerberg welcomes regulation

3:57 p.m.: Sen. Lindsey Graham grilled Zuckerberg about a lack of competition and asked him if his company is a monopoly. "It certainly doesn't feel that way to me," Zuckerberg responded.

Graham then asked if Facebook would welcome regulation. "I think if it's the right regulation, then yes," Zuckerberg said.

Wired editor-in-chief and CBS News contributor Nick Thompson said Graham's question was the toughest of the afternoon.

"That's the hardest question and Zuckerberg doesn't have an answer because they effectively do have a monopoly. So Graham's follow-up -- how do we trust you self-regulate if you're a monopoly? -- that's one of the hardest questions," Thompson said.

He believes Congress will face a decision about regulation, and predicted there will probably be regulation on ads and "maybe" on privacy, but said it could get intense if Congress deals with antitrust regulation.

Zuckerberg doesn't know if employees were involved with Cambridge Analytica

3:47 p.m.: Zuckerberg tells Sen. Maria Cantwell he doesn't know that his employees were involved with Cambridge Analytica's work with the Trump campaign ahead of the 2016 election.

"Senator, I can certainly have my team get back to you on any specifics I don't know sitting here today," Zuckerberg said.

Cantwell also asked if European privacy regulations should be applied in the U.S.

"Senator, I think everyone in the world deserves good privacy protection," Zuckerberg responded.

Zuckerberg: Facebook is cooperating with special counsel investigation

3:40 p.m.: Asked by Sen. Patrick Leahy about whether Facebook has received subpoenas from special counsel Robert Mueller's office as part of his investigation into Russian meddling, Zuckerberg first said the company had been subpoenaed and employees -- but not himself -- had been interviewed by investigators. He then clarified that he was not aware of specific subpoenas but said Facebook is cooperating with the investigation, work he said is "confidential."

Facebook played a prominent role in Mueller's February indictment of 13 Russians accused of interference surrounding the 2016 presidential election. The Russians are accused of using fake accounts, including on Facebook, to manipulate opinions.

"There will always be a version of Facebook that is free"

3:38 p.m.: Responding to a question from Sen. Orrin Hatch, Zuckerberg said there "will always be a version of Facebook that is free."

"It is our mission to try to help connect everyone around the world and bring the world closer together," Zuckerberg said.

"If [a version of Facebook will always be free], how do you sustain a business model in which users don't pay for your service?" Hatch asked.

"Senator, we run ads," Zuckerberg responded.

Facebook stock spikes higher during testimony

3:17 p.m.: So far, investors like what they're hearing. Facebook shares jumped 4.5% to $165 a share on Tuesday as Zuckerberg was answering questions. That's still down about 11% from the Friday before the Cambridge Analytica story broke on March 17.

Facebook didn't notify FTC about data misuse

3:10 p.m.: Responding to Sen. Nelson, Zuckerberg admitted that no one at Facebook notified the FTC about the data misuse in 2015. Zuckerberg said his company "considered it a closed case" after he told Cambridge Analytica and GSR to delete the illicit data.

Zuckerberg also said his company didn't consider notifying users of the misuse because they thought the issue had been handled.

Zuckerberg can't say how many other apps have misused data

3:02 p.m.: In response to a question from Grassley about other possible misuses of user data by outside developers, Zuckerberg said the company was still investigating apps that accessed user data before the company restricted access in 2014.

Zuckerberg said his company would be investigating "tens of thousands of apps" for suspicious activity. He said apps that misused data would be banned from the platform, but couldn't provide an exact number of apps that have been removed.

"As for past activity, I don't have all the examples of apps that we have banned here, but if you'd like, I can have my team follow up with you after this," he said.

Zuckerberg reads opening statement

2:53: Zuckerberg is delivering his opening statement: "We face a number of important issues around privacy, safety and democracy, and you will rightfully have some hard questions for me to answer."

"It is clear now that we didn't do enough to prevent these tools from being used for harm as well," he continued. "That goes for fake news, for foreign interference and hate speech."

Zuckerberg said his company "didn't take a broad enough view" of its responsibility and called it a "big mistake" that he's sorry for.

Lawmakers make opening statements before questioning

2:47 p.m.: Sen. John Thune, R-South Dakota, said in his opening statement that Facebook's "incredible reach" and what Zuckerberg described as a "breach of trust" is the cause for the hearing.

"The fact that those 87 million people may have technically consented to making their data available doesn't make most people feel any better," Thune said.

"In many ways you and the company you've created represent the American Dream," he added. "At the same time, you have an obligation to ensure that dream doesn't become a nightmare for the scores of people who use Facebook."

Sen. Bill Nelson, D-Florida, cuts to the chase: "If you and other social media companies do not get your act in order, none of us are going to have any privacy anymore. That is what we are facing,"

"If Facebook and other online companies will not or cannot fix the privacy invasions, then we are going to have to -- we the Congress," Nelson said. "How can American consumers trust your company to be caretakers of their most personable and identifiable information?"

Zuckerberg arrives

2:38 p.m.: Zuckerberg has arrived in the hearing room Tuesday to testify in front of Congress where he will face questions about his company's role in the mishandling of data of tens of million Facebook users.

​How much has the controversy hurt Facebook's stock price?

Facebook's (FB) stock remains at a low not seen since July 2017. Its stock closed at $185.02 a share on March 16, the Friday before revelations about the data scandal. The price started dropping on Monday and continued to fall over the following week.

On March 26, the FTC announced it was investigating whether Facebook violated an earlier settlement. The following day, Facebook's stock bottomed out at $152.20. Shares have slowly climbed back to about $160, down about 14 percent since the scandal broke. That represents some $60 billion in market value.

Read more at MoneyWatch.

​Twitter endorses Honest Ads Act

1:51 p.m.: Twitter announced Tuesday that it was joining Facebook in supporting the Honest Ads Act, a bill that would require online political ads to disclose who paid for them -- a requirement that is already in place for ads on TV and in print.

On Friday, Zuckerberg announced his support of the bill that was introduced by a bipartisan group of senators in October.

"Election interference is a problem that's bigger than any one platform," Zuckerberg said in a post, "and that's why we support the Honest Ads Act. This will help raise the bar for all political advertising online."

Cambridge Analytica launches CambridgeFacts.com

12:54 p.m.: Cambridge Analytica launched CambridgeFacts.com Tuesday in an attempt to explain its role in the Facebook data controversy. In an eight-point list, the data firm said Global Science Research (GSR) licensed Facebook data from 30 million individuals "trusting that it complied with Facebook's terms."

It said the company "contractually committed to only obtain data in accordance with the U.K. Data Protection Act and to get the informed consent of each respondent."

The firm said it deleted the raw data after Facebook asked them to and did not use it for the EU referendum or the 2016 U.S. presidential election.

Instead, the company said it used voter files from the Republican National Committee (RNC), polling data and "data available to their commercial brokers.""In truth, we used the same kind of political preference models used by the Obama and Clinton campaigns; however, we started five months out from election day and did it with far fewer resources and less data," the company said.

Who's asking the questions?

Here are the committee members that are set to pose questions to Facebook's Zuckerberg on Capitol Hill:

Senate Judiciary Committee members

Sen. Chuck Grassley, R-Iowa, Chairman

Sen. Dianne Feinstein, D-California, Ranking Member

**serves on both committees

Republicans

Sen. Orrin Hatch R-Utah, Sen. Lindsey Graham, R-South Carolina, Sen. John Cornyn, R-Texas, Sen. Michael Lee, R-Utah** ,Sen. Ted Cruz, R- Texas**, Sen. Ben Sasse, R-Nebraska, Sen. Jeff Flake, R-Arizona, Sen. Mike Crapo, R- Idaho, Sen. Thom Tillis, R- North Carolina, Sen. John Kennedy, R-Louisiana

Democrats

Sen. Patrick Leahy,D- Vermont, Sen. Dick Durbin, D-illinois, Sen. Sheldon Whitehouse, D- Rhode Island, Sen. Amy Klobuchar, D-Minnesota**, Sen. Chris Coons, D-Delaware, Sen. Richard Blumenthal, D-Connecticut**, Sen. Mazie Hirono, D-HawaiI, Sen. Cory Booker, D- New Jersey, Sen. Kamala Harris, D-California

Senate Commerce, Science and Transportation Committee members

Sen. John Thune, R-South Dakota, Chairman, Senate Commerce Committee

Sen. Bill Nelson, D-Florida, Ranking Member, Senate Commerce Committee

**serves on both committees

Republicans

Sen. Roger Wicker, R-Mississippi, Sen. Roy Blunt, R-Missouri, Sen. Ted Cruz, R-Texas**, Sen. Deb Fischer, R-Nebraska, Sen. Jerry Moran, R-Kansas, Sen. Dan Sullivan, R-Alaska, Sen. Dean Heller, R-Nevada, Sen. Jim Inhofe, R-Oklahoma, Sen. Mike Lee, R-Utah**, Sen. Ron Johnson, R-Wisconsin, Sen. Shelley Moore Capito, R-West Virginia, Sen. Cory Gardner, R-Colorado, Sen. Todd Young, R-Indiana

Democrats

Sen. Maria Cantwell, D-Washington, Sen. Amy Klobuchar, D-Minnesota**, Sen. Richard Blumenthal, D-Connecticut, Sen. Brian Schatz, D-Hawaii, Sen. Ed Markey, D-Massachusetts, Sen. Tom Udall, U-New Mexico, Sen. Gary Peters, D-Michigan, Sen. Tammy Baldwin, D-Wisconsin, Sen. Tammy Duckworth, D-Illinois, Sen. Maggie Hassan, D-New Hampshire, Sen. Catherine Cortez Masto, D-Nevada, Sen. Jon Tester, D-Montana

Thune: "It's time for Congress to exercise some oversight"

Sen. John Thune, R-South Dakota, says its time for Congress to step in and "exercise some oversight" on the issue of data privacy as Facebook CEO Mark Zuckerberg is set to testify on Capitol Hill on the protection of its users' data in the wake of the Cambridge Analytica scandal.

While lawmakers are just asking how Facebook allowed for political consulting firm Cambridge Analytica to obtain data on as many as 87 million users, some politicians are now questioning if regulations should be in place to prevent similar cases of data harvesting from ever happening again.

"We'll determine after we do that whether or not there are steps that need to be taken in the form of regulation or legislation going forward, but right now we want to get the answers and we think Facebook needs to be accountable, transparent and I'm glad Mr. Zuckerberg is appearing today," Thune told "CBS This Morning" on Tuesday.

CBS News poll: Americans not pleased with Facebook response

Americans say they were not surprised to learn that outside companies were accessing personal data of Facebook users, but they think Facebook's response so far has been unacceptable and believe the company could be doing more, according to a new CBS News poll.

Americans voice concern over the matter, but fewer than half say it concerns them a great deal. Most do call for more government regulation of social media and tech companies in an effort to keep their data private.

Of those polled, 61 percent have little or no faith that Facebook will sufficiently protect personal data in the future.

Prepared testimony released

On Monday, the House Committee on Energy and Commerce posted Zuckerberg's prepared testimony, in which the 33-year-old billionaire said his company needed to do more to protect the privacy of its users.

"We didn't take a broad enough view of our responsibility and that was a big mistake," Zuckerberg said in the testimony. "It was my mistake, and I'm sorry. I started Facebook. I run it, and I'm responsible for what happens here."

Cambridge Analytica

The full testimony directly discusses Cambridge Analytica immediately on page two. In it, Zuckerberg discusses what happened and what Facebook is doing about it. He blamed a Cambridge University researcher named Aleksandr Kogan for sharing personal data with Cambridge Analytics, against Facebook policies.

Zuckerberg then outlined the steps Facebook is taking to make sure this kind of situation doesn't happen again. These steps include:

• Safeguarding the Facebook platform to prevent developers from gaining "as much information"
• Investigating every app that had access to large amounts of data before 2014
• Building "better" controls to help users understand which apps have access to personal data

Russian Election Interference

Zuckerberg's testimony also includes references to the Russia's interference with the 2016 U.S. presidential election. Again, his testimony outlines what happened and how Facebook is changing because of it.

"We were too slow to spot and respond to Russian interference," says Zuckerberg. "We will continue working with the government to understand the full extent of Russian interference, and we will do our part not only to ensure the integrity of free and fair elections around the world, but also to give everyone a voice and to be a force for good in democracy everywhere."

Going forward, the Facebook CEO stated they are taking the following steps:

• Building new technology to prevent abuse
• Adding personnel for "security and content review"
• Strengthening advertising policies to increase transparency
• Sharing election integrity information about threats to U.S. and foreign governments