Should social media companies ban certain content?

Facebook, Twitter, YouTube and Microsoft to join hands and filter out content they consider "terrorist propaganda".

Social media has become an important part of our lives, galvanising protesters and driving elections.

Some of the world's biggest social media companies want to battle against what they consider "terrorist propaganda" online.

Facebook, Twitter, YouTube and Microsoft want to create a database of "digital fingerprints", which will flag content that is considered offensive or violent.

That includes recruitment videos for armed groups or gruesome imagery.

Once one bit of content is removed by one company, others can quickly follow suit, the companies hope.