IT systems used by the NHS are increasingly vulnerable to attacks by hackers attempting to extort ransoms from hospitals, according to reports.
At least 28 NHS trusts in England have been victim to ransomware incursions in the last 12 months, according to figures handed to the i newspaper in a Freedom of Information request.
NHS Digital, the body which looks after cyber-security in the health service, admitted there had been an increase in attacks but said that no ransom was paid and no data was lost.
It said patient records had not been affected and added that other organisations had also been attacked.
Ollie Whitehouse, technical director of NCC Group, the company that obtained the data, told the i: "Ransomware has become the bottom line of cyber-crime - if hackers break into a system and can't find any other way to monetise what they find, they encrypt the data and demand a ransom.
"We have seen a 400% increase in these attacks. The health service is by no means alone in facing this kind of attack.
"But NHS trusts are being increasingly targeted and any loss of patient data would be a nightmare scenario. Like everyone else, they need to be applying robust controls."
Ransomware works by implanting a piece of software, often sent in an email, which locks the user out of the system or files.
Hackers then demand a ransom using BitCoin, which can add up to thousands of pounds.