Excel spreadsheets containing the same information were also uncovered by the security expert, who didn't want to be named, while doing the same Google search. The audio files and spreadsheets were uncovered in a website directory that was not protected by a password and which Google had crawled and indexed for its search engine.

The files appeared to change often, indicating that perhaps only recent ones were kept in the public folder.

On Thursday afternoon, about eight of IF Telecom's recent voice contracts were listed in the folder.

IF Telecom operations manager Nick Holden told Fairfax Media on Thursday that the telco wasn't aware of the voice contracts being accessible on the public internet and thanked Fairfax for referring it to the breach.

"We're going to launch an investigation and we're going to take the site down immediately," Mr Holden said.