He has just launched his campaign to become the next president of the United States, but when he was a teenager, Beto O'Rourke belonged to the oldest group of computer hackers in US history.

Key points: The former Texas congressman is vying for the 2020 Democratic presidential nomination

The former Texas congressman is vying for the 2020 Democratic presidential nomination In his youth he was part of a group that invented the word "hactivism"

In his youth he was part of a group that invented the word "hactivism" At the time Mr O'Rourke stole long-distance phone service and wrote online essays under the name Psychedelic Warlord

Members of the hugely influential Cult of the Dead Cow, jokingly named after an abandoned Texas slaughterhouse, have protected his secret for decades, reluctant to compromise his political viability.

Now, in a series of interviews featured in an upcoming book, Cult of the Dead Cow members have acknowledged Mr O'Rourke, a former Texas congressman who is vying for the 2020 Democratic presidential nomination, as one of their own.

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The group is notorious for releasing tools that allowed ordinary people to hack computers. It is also known for inventing the word "hacktivism" to describe human rights-driven security work.

After more than a year of reporting, author Joseph Menn persuaded Mr O'Rourke to talk on the record, which he did on the understanding the information would not be made public until after his Senate race against Ted Cruz in November last year.

"There's just this profound value in being able to be apart from the system and look at it critically and have fun while you're doing it," Mr O'Rourke said.

"I think of the Cult of the Dead Cow as a great example of that.

"I understand the democratising power of the internet, and how transformative it was for me personally, and how it leveraged the extraordinary intelligence of these people all over the country who were sharing ideas and techniques."

It is unclear whether the US is ready for an ex-hacker presidential contender who, as a teenager, stole long-distance phone service for his dial-up modem, wrote a murder fantasy, and mused about a society without money.

O'Rourke known as Psychedelic Warlord

The book marks the ex-congressman as the most prominent former hacker in American politics.

There is no indication Mr O'Rourke himself engaged in the edgiest sorts of hacking activity — breaking into computers or writing code that enabled others to do so.

After his active period in the late 1980s, the group became famous for releasing tools that allowed ordinary computer users to hijack other people's machines.

Though it was controversial, the resulting chaos forced Windows maker Microsoft to dramatically improve security.

Mr O'Rourke also acknowledged that, during those teenage years, he stole long-distance phone service to participate in electronic discussions.

Supporters of Beto O'Rourke cheer for the then-Senate candidate. ( Reuters: Mike Segar )

Others in the group committed the same offence and got off with warnings. The statute of limitations ran out long ago.

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When he was a teen, Mr O'Rourke also frequented sites that offered cracked software, but he said he later realised his habit was not morally defensible and he stopped.

In the group, Mr O'Rourke wrote online essays under the pseudonym Psychedelic Warlord that could provide fodder for political supporters and foes alike.

One mocked a neo-Nazi, while another, written when he was 15, was a short piece of fiction from a killer's point of view in which the narrator drives over children on the street.

'Hacker' for president?

The long-suppressed tale fills out an unusual portrait for a presidential aspirant.

Born to a prominent El Paso family and sent to a boarding school and an Ivy League college, Mr O'Rourke felt a misfit as a youth and played in a punk band before starting a small technology business and an alternative press outlet, launching him into local politics.

Mr O'Rourke came to national attention last year when he came within three percentage points of defeating Mr Cruz, energising new voters and taking in record donations for a Senate campaign while eschewing special-interest money.

Politically, Mr O'Rourke has taken some conventional liberal positions, supporting abortion rights and opposing a wall on the Mexican border.

But he takes a libertarian view on other issues, faulting excessive regulation and siding with businesses in congressional votes on financial industry oversight and taxes.

Beto O'Rourke gestures as he concedes to Senator Ted Cruz at his mid-term election night party in El Paso. ( Reuters: Mike Segar )

Chris Wysopal, a hacking veteran who founded tech company Veracode with a friend from the Cult of the Dead Cow, said he had been happily surprised to hear of Mr O'Rourke's history.

"We need people at his level who come from the hacking community and get it," he said.

"But it's rare to see someone from that background have the leadership and communications skills. It's hard to believe that we might even see a hacker run for president."

Reuters