More than $25 million has been stolen from Australian credit cards by overseas hackers, federal police say.

Australian businesses were targeted by the scammers, who obtained about half a million credit card numbers, the Australian Federal Police says.

"The compromise is believed to have involved approximately 500,000 credit cards and resulted in more than $25 million in fraudulent transactions," the AFP said today.

"The borderless nature of this crime type poses new and unique challenges for law enforcement."

The AFP says investigations are continuing and officers are working with police overseas.

"International and private sector cooperation is critical to the AFP's ability to target this type of compromise, which is a challenging and time consuming process," it said.