The cyber criminal potentially responsible for a devastating hack on Qantas has made contact with the airline.

Qantas last week confirmed the data of up to six million Australians had been stolen.

The stolen data included customers’ names, email addresses, phone numbers, birth dates and frequent flyer numbers.

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On Monday, a Qantas spokesperson confirmed a “potential cyber criminal” had reached out to the airline.

“As this is a criminal matter, we have engaged the Australian Federal Police and won’t be commenting any further on the detail of the contact,” the airline said.

“There is no evidence that any personal data stolen from Qantas has been released but, with the support of specialist cyber security experts, we continue to actively monitor.”

Qantas maintains there is no evidence private information of millions of customers has been stolen. Credit: AAP

Qantas CEO Vanessa Hudson apologised over the breach last week, admitting she understood it was a serious concern for the millions of Australians caught up.

“What I would first like to say is I acknowledge the impact to all our customers and, first and foremost, I’d like to apologise to them,” Hudson told 7NEWS.

“I know the stress that it has created for many, many millions of customers that we’ve had.”

The national carrier revealed on July 2 that a third-party platform used by one of its call centres had been targeted in a major cyber attack, resulting in the leak of personal customer details.

The airline was first alerted to the hack on Monday when it detected “unusual activity” in its system.

Names, phone numbers, dates of birth and email addresses are among the information believed to have been compromised.

Qantas confirmed scammers were already impersonating the airline in the wake of the attack and warned customers to be vigilant.

Qantas claims frequent flyer accounts were not compromised. Credit: AAP

“The incident occurred when a cyber criminal targeted a call centre and gained access to a third party customer servicing platform,” the airline said last week.

“There is no impact to Qantas’ operations or the safety of the airline.”

Qantas said it had detected “unusual activity” last Monday via a third party platform used by its contact centre.

“We then took immediate steps and contained the system. We can confirm all Qantas systems remain secure,” the airline said.

“There are six million customers that have service records in this platform.

“We are continuing to investigate the proportion of the data that has been stolen, though we expect it will be significant.

“An initial review has confirmed the data includes some customers’ names, email addresses, phone numbers, birth dates and frequent flyer numbers.”

Qantas confirmed customers’ credit card details, personal financial information and passport details were not held in the hacked system.

“No frequent flyer accounts were compromised nor have passwords, PIN numbers or log in details been accessed,” the airline said.

The national carrier said it was putting in extra security to restrict access to its systems.