Mark Zuckerberg is 'very concerned' about ISIS threats

Mark Zuckerberg has opened up about the threats made against him by ISIS supporters last week.

"I am very concerned but not because of the video," he told Mathias Döpfner, the CEO of German media giant Axel Springer. "There have been worse threats."

Zuckerberg met with Döpfner while he was in Berlin last week. Their wide-ranging interview was published in Die Welt am Sonntag on Sunday.

A few days before their meeting, a group of ISIS supporters published a 25-minute video threatening to take down Facebook (FB, Tech30) and Twitter (TWTR, Tech30) -- as well as their leaders. The video was created in response to efforts by both companies to stop terrorist activity on their platforms.

"If you close one account we will take 10 in return," reads one of the slides in the video. "And soon your names will be erased after we delete your sites."

A few years ago, a Pakistani extremist tried to get the Facebook founder sentenced to death because the company would not take down a Facebook group that encouraged people to draw pictures of the prophet Mohammed. The act is illegal in Pakistan. (A Facebook spokeswoman did not immediately respond to questions about how this issue was resolved.)

Zuckerberg sees a common theme in both of these threats. "I think the bigger issue is that what Facebook stands for in the world is giving people a voice and spreading ideas and rationalism," he told Döpfner.

Mark Zuckerberg speaks during a town hall Q&A in Berlin (Feb. 2016).

Combating hate speech and terrorist activity online has become a growing problem for social media platforms -- especially Facebook and Twitter.

Extremists find supporters in these large open forums, then use them to publish and distribute propaganda.

Facebook and Twitter try to limit the reach of these networks and materials by suspending accounts and removing posts. But often, their efforts are slow compared to how quickly new problems pop up.

On Twitter for example, many ISIS-related accounts are set up with follower networks -- groups of users that follow one another called "swarm accounts." When one account in the network gets shut down, the others remain active and their follower base remains intact.

Facebook's problem is its size. With 1.6 billion people on its network every month, the company has hundreds of regional problems to deal with, on top of the big international issues like the Islamic State.

"Our North Star is that we want to give the most voice possible to the most people," Zuckerberg said in the interview. "We work closely with governments and local organizations to be certain we are applying [Community Standards] appropriately for local conditions and to identify and remove hateful or threatening content."

For example, Zuckerberg says that Facebook now removes threatening speech toward migrants in Germany amid growing tensions over the Syrian refugee crisis.

Closer to home, he has also had to deal with the issues of racism and free speech at Facebook's corporate headquarters.