Experts are warning that there could be further ransomware cases this week after the global cyber-attack. So, what has happened and how can organisations and individuals protect themselves from such attacks?
What is the scale of the attack?
Ransomware – a malicious program that locks a computer’s files until a ransom is paid – is not new but the size of this attack by the WannaCry malware is “unprecedented”, according to EU police body Europol.
It said on Sunday that there were believed to be more than 200,000 victims in 150 countries. However, that figure is likely to grow as people switch on their computers on Monday if their IT has not been updated and their security systems patched over the weekend.
There are also many other strains of ransomware which cyber-security experts say they are seeing being given new leases of life.
In the UK, the NHS was hit hard, but by Saturday morning the majority of the 48 affected health trusts in England had their machines back in operation. The NHS has not yet revealed what steps it took.
The malware has not proved hugely profitable for its owners so far. The wallets set up to receive ransom payments – $300 (£230) in virtual currency Bitcoin was demanded for each infected machine – contained about $30,000 when seen by the BBC. This suggests that most victims have not paid up.