A cyberattack that caused port operations to grind to a halt at four container terminals should be subject to a federal probe as a union pushes for DP World to reveal what it knew about the risks.
The Dubai-controlled stevedore, which handles 40 per cent of the nation's international freight, closed its Sydney, Melbourne, Brisbane and Fremantle port operations after detecting a breach on November 10.
Trucks were left idling at port gates and the transfer of 30,000 containers was delayed, with the backlog still being worked through.
DP World on Monday confirmed there was reason to believe some of the data accessed could relate to worker information, but the nature and extent of the breach was still unclear.
"We have communicated these early findings to our employees including recommendations for early steps which can be taken in response," a spokesman told AAP.
"As our investigation progresses we will be contacting individuals directly as required."
The Maritime Union of Australia is calling on Home Affairs Minister Clare O'Neil to launch an investigation into local managers' knowledge about the risks of the attack on critical supply chain infrastructure.
The union described the shutdown as "one of the gravest failures of corporate governance in recent memory" and claimed the company did not apply security patches to its IT systems that would have addressed its vulnerability to an attack.
"This cyberattack was not a terrible accident but an appalling failure and the managers responsible should be held accountable," assistant national secretary Adrian Evans said.
The company is currently locked in enterprise agreement negotiations with its workforce, with DP World's Oceania director previously accusing the union of aggressively pursuing a 27 per cent pay increase while rejecting workplace changes that would ensure more productivity.
DP World said it was working closely with multiple government agencies, including the Australian Federal Police, and would continue to provide updates on the progress of the investigation.