NHS Digital says the attack "was not specifically targeted at the NHS and is affecting organizations from across a range of sectors".
Wanna Decryptor is a piece of malicious software that encrypts files on a user's computer, blocking them from view and threatening to delete them unless a payment is made.
Dr Tony Naughton, the chief clinical officer at Fylde and Wyre CCG, described the problem as "national", while East and North Hertfordshire NHS Trust said it believed it had been hit by a "cyber attack" and had suspended all non-urgent activity.
But those attacks - blamed on Russian Federation, which has repeatedly denied them - followed an entirely different modus operandi involving penetrating the accounts of individuals and political organizations and then releasing hacked material online.
Britain's opposition Labour Party said the attack on English hospitals showed the need to place cyber security at the heart of government policy.
Power firm Iberdrola and utility provider Gas Natural were also reported to have suffered from the outbreak.
"At this stage we do not have any evidence that patient data has been accessed", the system says.
A global ransomware attack is holding more than 60,000 computers hostage.
Sushi lovers at risk of parasites in fish
Until recently cases in Western countries were rare because most dietary fish is cooked, which kills the worms . The larva was removed, and the patient's symptoms improved immediately , according to the BMJ report.
Whipps Cross Hospital, part of Barts Health Trust, has had to cancel routine appointments as a result, with hospital staff activating a "major incident plan".
The hackers are reportedly exploiting a critical vulnerability (MS17-010) that first received a patch on 14 March.
Screenshots of WannaCry with text in Spanish were also shared online.
In response to the attack Jonathan Martin, EMEA Operations Director at Anomali said: "This was an vulnerability waiting to happen".
"This was not targeted at the NHS, it's an global attack and a number of countries and organizations have been affected", Prime Minister Theresa May said.
"NHS Digital is working closely with the National Cyber Security Centre, the Department of Health and NHS England to support affected organizations and to recommend appropriate mitigations". Attacks occur regularly against Telefonica and today's wasn't major, the official said.
Affected NHS trusts said that IT systems had been shut down in order to protect them. Attacks of this kind have spiked in the previous year, jumping from 340,665 attacks in 2015 to 463,841 in 2016, according to Symantec.
Some frightening news out of the United Kingdom: someone has hacked the computers of the National Health Service and is demanding ransom.
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