Former Anonymous hacker-turned-FBI-informant Hector Monsegur warns that there is no real security, and if they wanted, hackers could break into airports, phone systems, and water supplies, and shut them down.

Giving his first interview since being outed as the hacker-turned-snitch, Monsegur, who called himself 'Sabu' when working with Anonymous and spin-off group LulzSec, asked "who will guard the guards?", and warned that security firms paid to protect citizens are themselves not entirely secure.

"In all reality there is no security," Monsegur warned during the interview, broadcast by CBS on 9 December. "Hackers could break right into the airport, the phone systems, obviously, the water supply systems - shut them down."

Recognising the documents leaked by Edward Snowden about government phone hacking, the informant went on: "We have a sickening reliance on security contractors, the companies Edward Snowden worked for. Who will guard the guards? Our security - the people we pay for, the people we hire with tax dollars - are not really secure themselves."

A career in hacking

From his bedroom in Lower East Side, New York, Monsegur began his self-taught career as a computer hacker by stealing credit card information and selling it to pay his own bills. He then adopted the Sabu name and joined the Anonymous collective of hackers and online activists.

One of Monsegur's early acts saw him hijack the Tunisian prime minister's website during the height of the Arab Spring, where he posted a letter in support of protesters. "It was amazing. I saw finally I was able to do something that contributed to society regardless if I was at home... behind a computer."

The 31-year-old said he felt little fear while hacking, because he always knew that once he had gone so far, he would eventually be caught. "After you're hacking for so long you reach a point of no return, regardless if you fear that they're gonna get you one day, it's too late."

Days after a hack on InfraGard, an FBI partnership with private business, Monsegur was arrested; he quickly chose to work as an informant and pass on all future interactions with Anonymous to the FBI, in return for avoiding up to 26 years in jail.

For the next three years he continued as normal, but with keyloggers recording everything he said to fellow hackers. Doing this, the FBI claims Monsegur helped prevent more than 300 cyber-attacks, such as those aimed at computer systems run by the military and Nasa.

"I was able to intercept attacks that were happening against the government and share it with the government so they could fix these issues," Monsegur said.

I didn't point the finger at my mates

Despite being branded a snitch and a traitor by his former Anonymous and LulzSec acquaintances, Monsegur insists he was not overtly giving names and personal information to the FBI. "It wasn't a situation where I identified anybody. I didn't point my fingers at nobody. My cooperation entailed logging and providing intelligence. It didn't mean 'can you please tell me the identity of one of your mates.'"

In May, Monsegur walked free from a New York courtroom, despite pleading guilty to taking part in cyber-attacks on Sony, Nintendo, Visa and Mastercard. The reason was what the court described as Monsegur's "extraordinarily valuable and productive" cooperation with an FBI investigation into his former Anonymous colleagues.