Report alleged Sellafield IT systems were attacked by hacking groups linked to Russia and China
IT systems and phone lines are down
Care centres are closed from California to Rhode Island
But 'most' services are designed to operate offline
Firm says the threat actor was 'sophisticated' and 'persistent'
Executives first said hack was 'Just a small breach'
Black Cat hackers claim that the data obtained from Barts Health NHS Trust represents the 'more bigger leak from the health care system in UK'
Related to University of Manchester attack earlier this month