Leicester City Council says more data stolen during the recent cyber-attack has been published.
The council shut down its IT networks on 7 March when its monitoring systems detected that an incident had taken place. They are now back online.
The council says it was a highly sophisticated attack by a known ransomware group who have hit a number of government, education and health organisations around the world, and are part of a global criminal investigation.
Richard Sword, the council’s strategic director of city development and neighbourhoods said: “Cyber security and police experts working with the council informed us yesterday that another batch of stolen data had been published.
“At 1.3 terabytes, this is a much larger batch of data than the 25 documents published last week. We are in the process of reviewing the data to see exactly what it consists of, and have notified the Information Commissioner of our actions.
“We have a duty to inform anyone considered at high risk as a result of data breaches. Due to the amount of data published, we will be prioritising people who may come under this category.
“We realise this data breach will cause concern, and apologise for any distress caused.
“We continue to work with Leicestershire Police and the National Cyber Security Centre as part of this investigation.”
Advice on action to take following a data breach is on the National Cyber Security Centre's website here: Data breaches: guidance for individuals and families - NCSC.GOV.UK
Frequently asked questions about the cyber attack are on the council's website here: Cyber Incident FAQs (leicester.gov.uk)