The program, described as “ransomware”, has encrypted data on the infected machines and will only release it if the sum is paid.
Yesterday, Lincolnshire County Council said on Twitter: “The Customer Service Centre is still running a limited service due to a malware attack. Please only call if absolutely necessary. Thanks.”
Although exact details of the data breach have not been disclosed, chief information officer Judith Hetherington-Smith reassured residents, noting that the council are “absolutely looking after their data and it hasn’t been compromised”.
he told the BBC: "It happened very quickly. Once we identified it we shut the network down, but some damage is always done before you get to that point - and some files have been locked by the software.
"People can only use pens and paper, we've gone back a few years.”
"A lot of the files will be available for us to restore from the back-up."
Lincolnshire Police have confirmed they are investigating the attack.
The Information Commissioner's Office, which is responsible for enforcing the Data Protection Act 1998, said it was aware of the incident.