A hacking group closely tied to North Korea was behind the massive WannaCry attack earlier this month, security company Symantec says.
The way the attack was set up made it "highly likely" that the Lazarus group was responsible, it said.
Lazarus has been blamed for a 2014 attack on Sony and the theft of $81m (£62m) from Bangladesh's central bank.
In those attacks, the group is believed to have worked on behalf of North Korea's government.