Jeanavive McGregor

The Australian Navy had only one battle-ready submarine at the start of this year as it struggles to keep its ageing fleet in the water, raising doubts over its ability to run a far more complex nuclear program. The navy insists its six Collins Class submarines, which this year cost $740 million to run, remain a "lethal capability", but a Four Corners investigation has found it has failed to meet crucial operational targets over the last two years.

Authorities are still tight-lipped about who carried out last year's Medibank hack that left the personal details of millions of Australians exposed on the dark web. However, security researchers have linked the attack to REvil — one of the most successful cyber gangs of all time. With the help of those researchers, we spoke to a hacker who says he's worked for them. Known as "Kerasid", he agreed to chat on an encrypted service. Four Corners: How do you feel when you hack into a system?

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