A shutdown triggered by a cyber security incident at major ports operator DP World Australia is still to be resolved.
The logistics company closed its Sydney, Melbourne, Brisbane and Fremantle port operations after detecting the breach on Friday.
The federal government is helping co-ordinate the stevedore's response, with Home Affairs Minister Clare O'Neill taking to social media to say the Australian Cyber Security Centre was also providing technical advice.
DP World Australia says it is working around the clock to restore normal operations.
"The company took immediate action, including disconnecting their internet connectivity, which stopped any ongoing unauthorised access to their network," it said in a statement on Saturday afternoon.
"This has also resulted in key systems, which underpin operations at their Australian ports, to not function normally."
It said the action was necessary to contain the incident and minimise impact on workers, customers, suppliers and other stakeholders.
As a result, landside access to the impacted ports has also been restricted.
"DP World Australia is collaborating closely with government and private sector stakeholders to ensure that sensitive inbound freight can be prioritised and retrieved," it said.
Parent company, UAE-based logistics giant DP World, employs more than 100 staff across more than 70 countries.
Its Australian operation is the country's largest.
