Thousands of Telstra customers personal data like names, addresses and phone numbers were uncovered online on spreadsheets by Lee Gaywood, owner of SMB marketing, yesterday.
The business owner stumbled over the data when looking for area access codes and Googled the word 'Telstra' and two other unnamed terms.
Gaywood, who contacted Fairfax Media
about the find, said he "couldn't really believe what I was looking at".
Almost 10,000 customers details were leaked - some just names, addresses and others with phones numbers and plan details, according to the report.
Telstra is no stranger to leaks of customer details online - something similar happened last year, and the telco has been investigated by the Privacy Commissioner several times. SmartHouse contacted the Privacy Commissioner and are awaiting a reply.
Peter Jamieson, Telstra's Executive Director Customer Service, issued a grovelling apology to customers today in a blog, admitting it was "unacceptable."
"When we learnt some of our customers' details were publicly available we immediately convened a team to have access to the data removed and commence an investigation."
Jamieson said Telstra "takes seriously" the confidentiality of customers' data, and says a team worked "round the clock last night looking through the data and trying to pinpoint how this actually happened."
While some of the information is generally available, such as names, addresses and telephone numbers up to six years old, Telstra are "acutely aware...some of the information may be sensitive to some."
"I apologise and assure everybody that we'll find out exactly what has happened here and do everything we can to make sure this does not happen again."
"We have sophisticated tools and techniques and skilled people working on risks and privacy-related projects protecting the security of our customers' information.