Air Vice-Marshal Darren Goldie said the firm, which has clients at government level in every state and territory, was working with the government to address impacts from the April breach.
"A number of Australian Government entities have been impacted by the HWL Ebsworth cyber incident, with sensitive personal and government information released," Air Marshal Goldie said in a statement posted to Twitter on Wednesday.
"I am actively engaging with HWL Ebsworth to understand the complete picture of this incident, including how their private industry clients have been impacted, as the data analysis continues."
Affected individuals are being notified about the impacts of the data breach, he added.
"We will work to ensure the lessons from this incident are shared so that we can continue to collectively bolster our responses to cyber incidents," Air Marshal Goldie said.
Hackers from Russia claimed last month to have published data from the HWL Ebsworth breach on the dark web.
The firm confirmed then it was investigating the claim.
Along with government departments and agencies, HWL Ebsworth counts some of Australia's biggest banks among its clients.
Air Marshal Goldie was appointed to the role of national cybersecurity co-ordinator last month.
At the time, Home Affairs Minister Clare O'Neil said a lack of co-ordination against cyber threats had left Australians at a disadvantage to attackers.
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