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Social media giants Facebook, Twitter, YouTube and Microsoft said Monday they have created a joint forum to remove extremist content from their respective services.

The companies -- under pressure after a rash of terrorist attacks -- said they would work together to improve and refine existing shared efforts for identifying and removing terrorist content, work with counter-terrorism experts and commission research to guide future decisions regarding removal of terrorist content.

"We believe that by working together, sharing the best technological and operational elements of our individual efforts, we can have a greater impact on the threat of terrorist content online," the companies said in a joint statement.

The Global Internet Forum to Counter Terrorism aims to "formalize and structure existing and future areas of collaboration between our companies and foster cooperation with smaller tech companies, civil society groups and academics, governments and supra-national bodies such as the EU and the UN," the companies said.

Social media sites have become a popular conduit for terrorist groups to share their ideas and recruit people to the cause. These companies have strict rules against posting hate speech and will remove such content and accounts when they're discovered. But the task of searching through the activity of hundreds of millions of users is daunting.

Facebook said it aims to be hostile to terrorists and pledged to "aggressively remove terrorist content" after an attack in London earlier this month killed eight people dead and left 48 wounded. In March, Twitter said it suspended 376,890 accounts in the last six months of 2016 for promoting terrorism.

Part of the forum's efforts will be directed at improving a joint database of images and videos that promote terrorism. The database, announced in December, stores and shares among partners the "hashes" -- or unique digital fingerprints -- of terrorist content that has been removed from the services for violating their community policies.

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