Two-thirds (64%) of London boroughs have suffered a data breach in the last four years, according to a Freedom of Information (FoI) request from cloud security vendor Secure Cloudlink.
The request was sent to all 32 London boroughs and the City of London authority to find out how well they protect their data, though Kensington & Chelsea and Hackney councils refused to disclose any information.
However, 21 out of the 31 respondents confirmed they have experienced a data breach in the past four years, including Barnet, Camden, Croydon, Greenwich, Lambeth, Lewisham, Wandsworth, Westminster and the City of London itself.
Bexley, Bromley, Ealing, Enfield and Haringey are among those that reported no breaches in the same timeframe.
No council said user accounts were hacked in the four-year period covered by the FoI.
Mark Leonard, chairman at Secure Cloudlink, said that the "sheer number" of councils that have been breached is "astonishing and reveals the issue of security is more prevalent than ever".
"There is a mass market for stolen data and hackers have become increasingly sophisticated in their tactics," he added. "Despite cybersecurity falling higher on the government's agenda, the issue persists. Organisations need to be endlessly diligent when it comes to putting the correct procedures in place to alleviate the growing security risks."
