The justice secretary said authorities were monitoring extremism and those accessing the material on the internet “with maximum energy and vigour”.
Police investigating the killing of Conservative MP David Amess fear the suspect may have been radicalised online during Covid lockdowns.
“There is certainly an element of more people at risk or vulnerable of radicalisation with spending more time online,” Mr Raab told Sky News.
“I’m absolutely confident that the intelligence agencies and the police are monitoring that with maximum energy and vigour.
“I know from my time working on the national security council and foreign secretary and now how hard they work. But of course they have to adapt to a different set of circumstances. They are on the case and they do an incredible job.
“But what you are seeing is behaviour morphing and changing and obviously we have got to adapt and respond to that.”
The deputy Prime Minister also spoke about the abuse MPs face online describing it as “out of control”.
But he said he did not want to see MPs being too afraid to meet their constituents.
“The elephant in the room here is the amount of online hate we all get,” he said.
“The amount of vile abuse directed at MPs, particularly female MPs, has got to stop.”
The Prime Minister will lead tributes to Sir David in the House of Commons on Monday after his family urged people to be tolerant and “set aside hatred” in his memory.
MPs will be able to share their memories of the Conservative MP for Southend West for at least two hours after a morning of prayers and a minute’s silence at 2.30pm.
In a statement, published through the Metropolitan Police, Sir David’s wife, four daughters and son said: “Strong and courageous is an appropriate way to describe David. He was a patriot and a man of peace.
“So, we ask people to set aside their differences and show kindness and love to all. This is the only way forward. Set aside hatred and work towards togetherness.
“Whatever one’s race, religious or political beliefs, be tolerant and try to understand.
“As a family, we are trying to understand why this awful thing has occurred. Nobody should die in that way. Nobody.”