Sixteen NHS divisions have been simultaneously hit by a so-called "ransomware attack." Patients have been diverted and non-emergency cases asked to stay at home.
Several NHS divisions reported problems with their computer systems on Friday afternoon local time, while hospitals in London, northwest England and other parts of the country alerted patients to the temporary closures.
"We are aware of a major IT secure system attack. All IT systems have been temporarily shut down," Derbyshire Community Health Services said on Twitter.
NHS Merseyside in the north of England reassured its patients via Twitter that it was working to solve the problem.
Doctors in England posted accounts of the shutdown on Twitter, describing a ransomware attack.
The NHS later confirmed several hospitals' computer systems had been hit by the Wanna Decryptor ransomware variant, but that patient data had not been accessed.
"This attack was not specifically targeted at the NHS and is affecting organisations from across a range of sectors," NHS Digital, a division of NHS England that handles information technology issues, said in a statement.
"NHS Digital is working closely with the National Cyber Security Centre, the Department of Health and NHS England to support affected organisations and to recommend appropriate mitigations," the public body said.
Ransomware attacks more frequent
British hospitals have been hit by ransomware attacks before, with hackers typically encrypting files and demanding a bitcoin bounty to unlock the files. The malware typically spreads through networks.
In 2016 an NHS division canceled operations and diverted major trauma cases when it was hit by a virus.
Intel Security reported in 2016 that hospitals were increasingly being targeted by ransomware operations, with one operator earning almost US$121 million (111 million euros).
"A combination of legacy systems with weak security, a lack of employee security awareness, a fragmented workforce, and the pressing need for immediate access to information has led the criminal underground to prey on hospitals," the report said.
In 2016 British leaders unveiled a multibillion-pound national cybersecurity strategy that included new police units to target organized online gangs and even retaliation for major attacks.
Several hospitals in Germany were hit by ransomware attacks in 2016, but they were able to rely on backups to restore function.
aw/kms (AP, Reuters)