More goods could be held up at the nation's ports as dockers push on with industrial action against port operator DP World despite a devastating cyber attack.
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 Friday.
Trucks were left idling at port gates and the transfer of 30,000 containers was delayed, although the testing of crucial systems over the weekend allowed about 5000 containers to move out of the four terminals on Monday.
But amid strained pay negotiations, port operations were further disrupted from the afternoon as workers took planned protected industrial action.
The action included overtime bans, stop-works and restrictions on truck movements.
"Our members are dedicated, hard-working and loyal, and they will put their skill and commitment towards resolving the backlog caused by the cyber attack," Maritime Union assistant national secretary Adrian Evans told AAP.
"But they will not be made to work with a gun to their head while DP World's HR bosses continue to refuse to meet to finalise a new agreement."
DP World's Oceania director last week accused the union of aggressively pursuing a 27 per cent pay increase while rejecting workplace changes that would ensure more productivity.
The company on Monday warned its investigations and response to the cyber attack would cause further temporary, but necessary, disruptions this week.
"DP World Australia's investigation and ongoing remediation work are likely to continue for some time," it said.
Cyber Security Minister Clare O'Neil said the stevedoring company's incident underlined the nation's vulnerability to attacks.
But reforms introduced by Labor allowed for a whole-of-government response to the attack, in co-ordination with the company and federal police, she said.
"We've commenced a very substantial, very important set of national cyber exercises which help us flex and build that muscle," she said.
DP World has also alerted the Australian Information Commissioner as it assesses whether personal information is within the data stolen from its network.
Retailers and those representing their delivery networks said the disruption highlighted the need for investment in fortifying supply chains.
"We understand most retailers already have their Christmas stock holdings in the country, but retail is a 52-week-a-year operation and so any significant disruption to port operations is potentially harmful," Retailers Association chief executive Paul Zahra said.
Freight and Trade Alliance director Paul Zalai called for action on the Productivity Commission recommendations last year to address steep rises in the price of moving containers through ports.
DP World and two other operators in Melbourne jacked terminal access charges more than 10-fold between 2017 and 2022.
"We need the federal government to respond to that Productivity Commission report as that would go a long way to addressing the rising charges ... which is only adding fuel to inflation," Mr Zalai said.
Australian Industry Group chief executive Innes Willox said the disruption could result in shortages or flow-on effects for prices if the issue dragged on.
But independent economist Nicki Hutley said it was too early to say whether sluggish imports and exports could further fuel inflation as the disruption would need to drag on for "a very long time" for that to happen.
On Monday, the government announced two policy reforms to the upcoming national cyber-security strategy, including introducing mandatory reporting requirements for ransomware attacks.
