Telstra moved to assure customers over an incident where subscriber data was incorrectly made public, as it acknowledged some unlisted customers’ details were made available on directory assistance due to a misalignment of databases.

In a statement, CFO Michael Ackland explained Telstra recently detected an error which resulted in some customers’ names, numbers and addresses being listed when they should not have been.

After the discovery, he said Telstra began contacting impacted customers and removing their details from the directory assistance service and online version of the white pages, which it is required to provide as part of its regulatory obligations.

“We are conducting an internal investigation to better understand how it happened and to protect against it happening again,” Ackland said.

Reuters reported the personal information of 132,000 customers was exposed.

The breach is a latest in a spat of large-scale unauthorised disclosures of personal data in Australia.

In September, rival Optus was hit by a cyberattack which resulted in unauthorised access of current and former customers’ information.

A month later, Singtel’s local IT services consulting company Dialog Group’s servers were compromised in an attack involving access of some client and employee information.