A cyber criminal group has posted what it claims are documents stolen from Hackney Council in a ransomware attack.
The publication on the dark web of the personal details of council staff and residents follows “a serious cyber-attack” on the council in October.
Experts said the data was “limited” and “not visible through search engines”.
Officials continue to work with the UK National Cyber Security Centre and National Crime Agency to investigate the hack, the council said.
Hackney Council’s cabinet member for planning, Guy Nicholson, said the hack had affected services residents relied on, including by disrupting the ability of the council to process land search requests for those buying property.
The council said the vast majority of sensitive or personal information held by the council remained unaffected.
It added that it would support any directly affected people.
‘Worry and upset’
Hackney’s mayor Philip Glanville said the hack was “utterly deplorable”.
“I fully understand and share the concern of residents and staff about any risk to their personal data, and we are working as quickly as possible with our partners to assess the data and take action, including informing people who are affected,” he said.
“While we believe this publication will not directly affect the vast majority of Hackney’s residents and businesses, we are sorry for the worry and upset this will cause them.
“We are already working closely with the police and other partners to assess any immediate actions we need to take, and will share further information about the additional action we will be taking as soon as we can.”
In February last year, another local authority – Redcar and Cleveland Borough Council – was hit by a ransomware attack, which cost it more than £10m.