He was found lying in his parents' bed in their Collaroy home, wearing boxers and a T-shirt, with cocaine residue on his desk. ''It was just horrific, surreal,'' says Mrs Skelly, who rushed home from Vietnam with her husband Greg to face the death of her only child. ''I had never even seen him drunk, I never saw a single sign that he might be taking drugs.'' In a state of shock, Mrs Skelly started digging. First Facebook, then bank accounts. To her horror, she discovered her son was one of a growing number of young Australians buying drugs online in a murky hidden world that authorities and academics say is simply impossible to stop.

Daniel and his friends, a mix of mates from university, St Luke's Grammar School in Dee Why and Freshwater Senior Campus, chatted on Facebook about experimenting with new drugs and pooling their money to buy from anonymous websites such as Silk Road and similar online marketplaces that emerged when Silk Road was closed down by the FBI in October. Daniel had made five purchases over two years. On November 5, he bought $900 worth of cocaine from Sheep or Black Market Reloaded - both easily accessible websites listing page after page of illegal drugs, prescription medication, synthetic drugs and even guns. The websites only accept bitcoins, an encrypted online currency. The package arrived on the doorstep of the Skellys' Collaroy home the next day in an innocuous Express Post envelope. Mrs Skelly dug even further, finding that Daniel had regularly bought bitcoins from a Brisbane-based company called Cryptospend. He was told by the company to make cash deposits at NAB, Westpac or St George banks.

''I felt like I was drowning in a sea of evil,'' she said of her spiralling search into a world she had never heard of, let alone knew her son was dabbling in. However, Drug and Alcohol Research and Training director Paul Dillon said it was a world that tech-savvy youths are increasingly delving into online. Nearly one in 10 respondents to the 2013 Global Drugs Survey said they had bought drugs online. ''They live in a digital world and they're certainly getting information about drugs through the internet, so it's no surprise they're also purchasing them through the internet,'' Mr Dillon said. ''I ask kids whether they worry that a police officer will be waiting for them when they go down to the post office and the response over and over again is, 'Well, you only live once.'''

Dee Why police said Daniel's death was still under investigation and a report would be forwarded to the coroner. Autopsy results are not complete and toxicology tests show non-lethal levels of cocaine. However, it was cut down with the potentially lethal agent Levamisole. Desperate to make some sense of her son's death, Mrs Skelly has launched a petition on change.org, calling on the government to outlaw encrypted bitcoin transactions. A spokeswoman for federal Treasurer Joe Hockey said he ''understood the basis'' for her campaign but believed any regulation should be instigated at an international level. Acting Treasurer and Minister for Small Business Bruce Billson said: ''Given the tragic nature of the case, it would be unfair and inappropriate to make comment without having a good look at the issues to enable a considered response following the family's loss.''

Mrs Skelly is determined to let other parents know what she wishes she did earlier. ''My husband and I think we haven't got anything else to lose,'' she says. ''We've already lost something pretty huge.'' Safety starts in education Cracking down on websites selling illegal drugs is virtually impossible, police say. The sites require users to download a program that channels their internet connections through a complex international web of proxy servers that conceal their identities.

They use anonymous internet ''bitcoins'' and products are sent inconspicuously in regular mail with phoney return addresses. When Silk Road was closed down by the FBI in October, countless sites took its place. ''We can't be in people's living rooms or next to a 16-year-old with a smarpthone,'' the NSW Drugs Squad Commander, Detective Inspector Nick Bingham said. ''It's virtually unpoliceable. We need parents to educate their kids of the dangers.'' Drug educator Paul Dillon said accessing the sites was not as simple as typing in a web address but if young people did not know how to do it, they almost certainly knew a friend who did.

''Trying to outlaw these sites is like trying to put your finger into a hole in a dam,'' he said. National Drug and Alcohol Research Centre online drug markets expert Lucy Burns said the only approach was to educate young people.