Residents in some of Sydney's richest neighbourhoods may have had their personal information and some credit card details stolen in a pre-Christmas hack on a council's libraries.
Woollahra Council, which includes harbourside suburbs in Sydney's east like Double Bay and Point Piper - home to former Prime Minister Malcolm Turnbull - said it learned of a cyberattack on its systems on December 15.
Council don't know how many people have been affected, but confirmed the hacker "may have been able to access some of our customer's personal information".
There are three libraries in the council area; Double Bay, Watsons Bay and Paddington.
Woollahra Council said the kind of information stored, and possibly exposed, includes people's names, addresses, email addresses, phone numbers and partial credit card payment details.
The incident, which targeted a third-party software system, only impacts library card holders who have accessed library computers, room bookings, printing and scanning or the payment of any library fines.
The system also stored encrypted passwords used to access the booking system.
Council is working with the Australian Cyber Security Centre, Cyber Security NSW and a specialist cyber forensic firm to investigate the incident.
"The provider of the software that was breached developed a software fix to the address the vulnerability in their system," a council spokesperson said.
Council has been contacting affected library users since last Friday, advising people what to do next.
The government agency ID Support NSW can be contacted on 1800 001 040.