The National Security Agency (NSA) has linked the Wannacry ransomware which swept the world last month to North Korea.
The cyber attack in May affected more than 200,000 computers in 150 countries, and severely affected hundreds of organisations and companies like the NHS, which was one of the most high-profile victims.
Affected computers were held hostage, with the hijackers demanding the payment of a bitcoin ransom to restore operations. The type of action it used to hijack the computers, called EternalBlue, was believed to have been developed by the NSA itself.
Now, the agency has produced a report of the incident which links a hacking group affiliated to North Korea to the attack.
The Washington Post is reporting that, while the evidence is not conclusive, it strongly suggests North Korean involvement.
The findings have been supported by security firm Symantec, but have been disputed by other companies.