Twitter has been misused for bulling by so-called trolls, but now there's a new threat of the worst kind.
Seven News can reveal criminals are using it to trade indecent photos and videos of children, and police can't stop them.
As a tool for bringing the world together Twitter is a modern marvel, with half a billion users sending 340 million messages each day.
Abusive internet trolls have hit the headlines recently, but now another sinister use has emerged.
Criminologist and former UK detective Mark Williams-Thomas says that at this point in time it is a ‘paedophile’s playground’.
"It's probably one of the biggest platforms offenders are targeting and now using in a very open way," Williams-Thomas
By entering code-words he showed Seven News a disturbing series of active accounts set up to trade illegal images of young children.
"These are keywords those are words known by those who have a sexual interest in children, they'll search on those keywords and they'll bring up certain users."
They will also post in their conversation either links or photographs of children being abused.
Williams-Thomas’s work formed a UK campaign against Twitter paedophiles, that led to arrests this month, and he has a warning for Australia.
"There will be people in Australia right now searching out other like-minded individuals in order to exchange share and discuss the sexual abuse of children," he says.
Twitter has said it is attempting to stop the illegal pictures being posted using new automated software that removes certain pictures, but critics say they're far too slow in shutting down that offending accounts.
Leading child protection advocate Hetty Johnston says the ?? is harming children.
"It's a case of supply and demand, the more demand through Twitter and other sites then the more supply there has to be," Johnston says.