Government bodies and other organisations could also be affected by the malware attack that brought down some NHS services, a cyber security expert has warned.
Companies operating large networks, thought to be particularly vulnerable, are being urged to make sure they are secure in the wake of the attack.
"Absolutely it's highly possible that as the days come forward unfortunately we are going to hear that more organisations and government bodies are going to have been affected," cyber security expert Paul Norris said.
"Unfortunately, it's going to be big names and it's going to be organisations that have got weakened security controls that are going to be mostly impacted by this."
Hospitals have stopped diverting patients following last week's cyber attack which crippled many NHS Trusts' IT systems.
A young computer expert from north Devon who was hailed a hero for helping to stop the global cyber attack said he was just "doing my bit".
One surgery has no access to medical records.