England’s biggest hospital trust has been hit by an "IT attack", potentially infecting thousands of files.

Barts Health NHS Trust reportedly sent staff an email this morning warning of a 'ransomware virus attack issue' that was being handled by engineers.

A trust spokesperson told Digital Health News on Friday morning that the trust was dealing with a "ransomware virus" and had shutdown parts of its IT system as a precaution. However, by 4.30pm a trust spokesperson said it was now unlikely that ransomware was involved and described it as a "IT attack".

“We are urgently investigating this matter and have taken a number of drives offline as a precautionary measure. We have tried and tested contingency plans in place and are making every effort to ensure that patient care will not be affected.”

As of 3pm on Friday afternoon, the trust said some drivers were still offline. The trust had established that neither the Cerner Millennium patient administration system and the clinical system used for radiology were affected.

He was not aware of the attack disrupting patient services across the trusts four hospitals in East London. He would not comment on how the trust was alerted to the attack or how it got onto the trust's systems.

According to HSJ, the attack has infected thousands of files stored on Window XP computers and parts of the network have been shut down while engineers investigate.

It is the second major disruptive cyber-attack on the NHS in the past three months..

Police are still investigating a ransomware attack at Northern Lincolnshire and Goole NHS Foundation Trust in November, that all but shut down the trust systems for four days, resulting in the cancellation of 2800 appointments. The trust did not pay the ransom.

It also comes against a backdrop of a rising cyber-security threat for the NHS, with concerns that many trusts still rely on legacy IT systems, such as Windows XP, that are vulnerable to attack.

In response to a Freedom of Information Act lodged by NCC Group in last year, 28 NHS trusts confirmed that had dealt with a ransomware attack in the past year.

Since the Northern Lincolnshire and Goole attack several trusts have been reviewing their cyber security and plugging gaps in their cyber sercurity.

On Thursday, Digital Health News reported that Sheffield Teaching Hospitals NHS Foundation Trust's new information technology strategy identified cyber threats as the biggest digital risk it faced.

“The infection can come from anywhere, sometimes even a trusted source, and therefore we need to be extra vigilant as a cyber-attack could be a case of life or death.”

Pete Banham, a cyber resilience expert at cyber security company Mimecast, said the Barts Health attack "reads like a textbook example".

Digital Health Intelligence is holding a Digital Health and Care Cyber Security Summit in London on 24 January. To learn more click here.