A gang of cybercriminals has published almost 400GB of stolen data on the dark web from an NHS blood testing company following one of the largest cyberattacks in UK history.

The gang has been trying to extort money from NHS provider Synnovis following the initial hack on 3 June. 

The stolen data includes patient dates of birth, NHS numbers, names and descriptions of blood tests. 

In a statement to the BBC, NHS England said it had “been made aware that the cyber criminal group published data last night which they are claiming belongs to Synnovis and was stolen as part of this attack.

“We understand that people may be concerned by this and we are continuing to work with Synnovis, the National Cyber Security Centre and other partners to determine the content of the published files as quickly as possible.

“This includes whether it is data extracted from the Synnovis system, and if so whether it relates to NHS patients.”

The Synnovis hack is one of the worst cyberattacks in UK history, with more than 1,000 hospital and NHS GP appointments affected by the disruption.

On 14 June, the NHS revealed that 97 cancer treatments and five caesarean sections had to be postponed. Additionally, 18 donated organs were redirected to other trusts and pathology services in south-east London were only operating at 10% capacity.

More than 800 planned operations and 700 outpatient appointments were postponed within the following week.

Synnovis was launched following a partnership between SYNLAB UK & Ireland, King’s College Hospital NHS Foundation Trust and Guy’s and St Thomas’ NHS Foundation Trust.

The global cybersecurity market will be worth $290bn by 2027, growing at a compound annual growth rate of 13% between 2022 and 2027, according to GlobalData’s Cybersecurity – Thematic Intelligence report.