DETROIT (AP) — In the wake of Britain's third major attack in three months, Prime Minister Theresa May called on governments to form international agreements to prevent the spread of extremism online.

Here's a look at extremism on the web, what's being done to stop it and what could come next.

Q. What are technology companies doing to make sure extremist videos and other terrorist content doesn't spread across the internet?

A. Internet companies use technology plus teams of human reviewers to flag and remove posts from people who engage in extremist activity or express support for terrorism.

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