Blackbaud, the provider cloud computing, was forced to notify dozens of charities, organizations and universities after falling victim to malicious agents in May.
The US company said that despite the breach, it has not detected leaks of bank accounts or payment information falling into the hands of criminals in the cyberspace, but confirmed that it paid a ransom to stop the destruction of its systems.
Jon Townsend, head of information for the charity, said: "We take our data protection responsibilities very seriously. As soon as we realized this incident, we started an internal investigation and worked with the third party vendor, Blackbaud, to assess whether further action was needed.
As the Office of the Information Commissioner announced yesterday, 125 organizations have been affected by the incident so far, however it is expected that this number will increase.
A number of universities and organizations, including Sue Ryder, the Disease Charity and Crisis, the charity for the homeless, is among those affected.
An ICO spokesman said: "BlackBaud has reported a case of data breach that may have affected a large number of UK organizations using its services and we are investigating."
"The organizations involved should contact their customers to let them know if their personal data has been affected."
The attack took place in May, but was discovered this month and has raised major privacy concerns, with Blackbaud saying hackers had copied a subset of data from its systems. Blackbaud said it had managed to stop them hackers block it from its system and encrypt its files. Pay them cybercriminals ransom for deleting the data and said he had received confirmation that the copy had been damaged.