Telstra has apologised after publishing the details of thousands of customers online.
The company said the release of the names, numbers and addresses of some unlisted customers was not the result of any malicious cyber-attack and was a mistake. Reports say up to 130,000 customers have been affected.
Telstra said a “misalignment of databases” meant the details of some unlisted customers were made available via directory assistance or the White Pages.
“For the customers impacted we understand this is an unacceptable breach of your trust,” Telstra executive, Michael Ackland, said.
“We’re sorry it occurred, and we know we have let you down.”
Telstra said it was working to pull the data from the internet.
Affected customers were being contacted and offered free services to combat identity theft.
“We are conducting an internal investigation to better understand how it happened and to protect against it happening again,” Ackland said.
The mishandling of customer data comes after data breaches at Optus and Medibank, where poor security processes allowed hackers to steal thousands of customers’ data.
The home affairs minister, Clare O’Neil, has previously criticised companies for poorly protecting customer data, as the government considers tougher laws on the handling of sensitive information and data hacking.
The incidents with Optus and Medibank raised questions about why companies were retaining sensitive data years after they no longer needed it.