Suspected North Korean hackers have recently tried to break into at least nine health organisations, including pharmaceutical giant Johnson & Johnson and vaccine developer Novavax Inc, revealing a broader effort to target key players in the race to develop treatments for Covid-19.

Four people who have investigated the attacks said the spate of hacking attempts began in September, with web domains mimicking online login portals used to try and trick staff at the targeted organisations into revealing their passwords.

The hacking attempts included a bid to get inside British drugmaker and vaccine developer AstraZeneca, which Reuters first reported last week was in Pyongyang's crosshairs...