Zuckerberg said at the hearing

Facebook's Chief Executive Mark Zuckerberg told the US senators that his organization is constantly fighting with Russian operators who are looking for opportunities to use Facebook.
Zuckerberg said it is a weapon competition. They are constantly improving.
Zuckerberg has to answer many questions before the US senators about fraud scandal related to UK's election consultancy firm Cambridge Analytics.

Investigating officers interrogated Facebook officials about the intervention of the Russian intelligence agency on Facebook in the 2016 US election. In February, US investigators identified 13 people and three Russian companies as election interveners.
Zuckerberg said there are many Russian people, whose work is to impersonate Facebook and other internet systems. Need to investigate further.
Meanwhile, Senators pressured Zuckerberg to control Facebook, he said, he wants control, that should be in the right rule. But he did not say anything about specific controls.
Zuckerberg appeared before the hearing in front of some joint committee of the US Senate after the information was received by Cambridge Approximately 8.8 million data from Facebook.
At the hearing, Zuckerberg also said:

• They did not do much to prevent Facebook's tools used to be harmful.
• Without checking, Cambridge Analytics has completely erased the information, it was wrong to believe it.
• Facebook does not believe that the singles dominate - Zuckerberg does not think such a thing.
• Always talk about launching a free version of Facebook, Zuckerberg
• He is not very concerned about the rate of Facebook mistakes in automatically identifying hate speech.
• Personally he is concerned about the possibility of political bias on Facebook.
• Facebook authorities are creating new tools to identify fake accounts.
  What is the Cambridge Analytics scandal?
  Cambridge Approach is better known for Donald Trump's support in the US presidential election in 2016. It is believed that the trump is played in its conquest of victory. However, the company claims that they did not use any information collected from Facebook to propagate Trump. Christopher Willie, a former UK based London-based Cambridge analyst, has brought the issue of unrecognized information to Facebook users.He was the first to say that the referendum on the question of US Presidential election and the breakthrough in the UK (separation from the European Union) was his former workplace. Cambridge University lecturer Alexander Leonid Kogan supported Cambridge Analyst. He created a special app on Facebook platform. Through this he collected personal information of millions of users and sold it to Cambridge Analyk.
  According to Christopher Willie, Cambridge analyzed the information provided to the Republican candidate Donald Trump's campaign camp in the US presidential election in 2016. Not only that, analyzing those data, potential Republican voters are also identified.
  It was initially believed that Cambridge Analytics has probably grabbed 5 million Facebook user data. However, this week, the Facebook authorities acknowledge that data of 80 million users is unaffected.
  Zuckerberg said in the hearing, "I started Facebook and I am responsible for everything."
  In the United States consisting of 44 Senators, in the joint hearing of the business leaders and trade and judicial committees of the lawmakers, he was seen wearing trimmings, T-shirts and jeans leaving the quotes. In the hearing on Tuesday for several hours, he also asked for forgiveness several times as well as promises for the restoration of privacy. The Senators challenged Zuckerberg's explanation in the hearing.
  Analysts say the lawmakers have expressed concern that strict control over Facebook may be imposed. References: BBC, NDTV, Washington Post.