Ports operator DP World Australia says it is working to contain a "cybersecurity incident".
The company, which manages container terminals in Sydney, Melbourne, Brisbane and Fremantle, said it detected the cybersecurity incident on Friday.
"Our teams are working diligently to contain the situation and determine the impact on our systems and data," DP World Australia said in a statement.
"To safeguard our employees, customers and our networks, we have restricted landside access to our Australian port operations while we continue our investigation.
"This is part of a comprehensive response which includes engaging with cybersecurity experts, actively investigating the incident and notifying the relevant authorities."