When users sign up to a new phone plan, in order to get that 'new phone feeling', they hand over their drivers' licence information, along with other details such as passport details and/or credit card information, and potentially sensitive data like marital status.

Well, not only is Telstra using this data to double check your identity and credit rating but also send you via the MCN advertising network, according to media reports today.

The reports say Telstra has 8.5 million customer IDs on hand in order to market to customers better,  MCN, which stands for the Multi Channel Network, the says that IDs are matched to a customers phone number or IP address, and customers are then served specific ads based on incredibly accurate date of birth and address information.

Telstra partnered with MCN back in 2012 to offer ads across the Telstra network.

MCN told The Australian it used an “ID targeting data platform” that could access a “highly accurate audience data set on consumers’ age, gender, postcode, income and more”.

MCN national digital sales director Nick Young said in an interview the platform relied on Telstra’s 100-point ID checks for its accuracy.

“About 50 to 60% of our audience has a Telstra ID,” Young said. “(That’s) around 8.5 million individuals.

“Through the fact that if you go into or buy a Telstra product you have to show 100 points of ID to get that, we know (the data is) correct. Because it’s based on a passport, it’s 99.9% accurate.

“Through the data matching process, we’ve matched each individual computer to that ID or that household address.”

Young said previously, demographic information about users was based on where they had been on the Internet.

“We look at where they’ve been and we overlay that with the Telstra data. We can add depth to that,” he said.

Telstra denied the reports to the newspaper, saying that it isn’t handing over detailed ID info for marketing purposes and that only postcodes and other basic information are provided.

The telco said information like detailed names and addresses are reportedly being redacted.

Either way, the news means Telstra is holding onto customers' drivers licenses, credit card info and passport details, meaning a hack like the many, many attacks we've seen in recent months can be considered a possibility. As for whether Telstra is actually using that information for its advertising... that's another question.