Telstra doesn't have the best track record for keeping data secure. "I couldn't really believe what I was looking at when I found the data," Mr Gaywood said. "I've worked in telcos before and I know that this sort of data should be kept very private and customers would expect it to be secured." He said he stumbled across the data after entering into the Google search field "Telstra" and two other search terms, which Fairfax has chosen not to name as the spreadsheets may still be cached on Google's search engine. Telstra took the files offline after being notified of the breach by Fairfax at about 4pm on Wednesday. Fairfax found approximately 1677 customer records in one of the spreadsheets, which contained Telstra customers' names, phone numbers, plan names and home addresses. A further three spreadsheets contained 8201 customer records that contained only names and telephone numbers, but not home addresses.

The spreadsheets also contained internal Telstra reference numbers relating to customer accounts. Other internal Telstra training documents were also found online via a similar Google search to Mr Gaywood's. The data appeared to be hosted on a server not belonging to Telstra but a third-party it uses. Telstra executive director of customer service, Peter Jamieson, thanked Fairfax for alerting it to the issue. He said the breach was "concerning" and that the data should not have been in the public domain. "This is unacceptable," Mr Jamieson said. "We take very seriously the confidentiality of our customers' information and we will take all steps to ensure we protect that information. [I'm] very disappointed about the fact that we have made available information about our customers on this occasion." Telstra was investigating exactly how the data was made available outside of its network, he said.