The volunteers using 'honeypot' groups to fight anti-vax propaganda

In a policy shift, Facebook is now removing groups and pages that discourage people from getting vaccines. As social media giants grapple with the anti-vaccine movement, Marianna Spring meets the everyday citizens battling conspiracy theories in their spare time.

The banner image shows a Photoshopped picture of Bill Gates with a crazed expression holding a needle decorated with a skull and crossbones. It looks like a Facebook group promoting anti-vaccine conspiracy theories.

But this group actually has very different intentions.

Richard is a builder, a trainee psychologist - and one half of the duo behind the decoy group. He says he aims not to spread bad information but rather to help people attracted to conspiracy theories.

His friend Dave (not his real name; we've agreed to give him a pseudonym because he fears abuse from anti-vaccine activists) believed in conspiracy theories for the best part of 20 years.

"If I was to actually create a group saying, 'I'm going to re-educate you'... then I'm not going to get any takers," he says.