"We're very, very attuned to it, because it's a critical supply chain to protect," Telstra chief executive Andy Penn told the National Press Club on Thursday.

A supply chain for a vaccine starts with the pharmaceutical company and extends through to transport and hospitals and clinics.

"There's malicious activity around all of those organisations all of the time," he said.

Mr Penn declined to go into detail about Telstra's efforts.

He said the attacker's motivation was often unknown and it was unclear whether it was specifically targeted at the vaccine supply chain itself or whether it was malicious activity targeted at a particular operator such as Australian logistics giant Toll Group.

Toll was infected with ransomware twice last year, which disrupted goods and service delivery across the country.

Telstra, Optus, and Woolworths were among those whose shipments were stopped when Toll was taken offline by cyber criminals.

The hackers also stole data before encrypting Toll's data and publishing on the dark web, which Mr Penn warned was the new modus operandi of cyber criminals.

Mr Penn couldn't rule out a successful attack on Australia's COVID-19 vaccine supply chain.

"I think it's likely that there will continue to be malicious activity that may or may not affect companies."

In 2019, several hospitals and clinics in Australia, often made vulnerable by old systems stitched together, were targeted by ransomware.

Access to patient records and contacts, as well as scheduling and financial management systems, were significantly impacted.

Asked whether Telstra was itself a target, Mr Penn said they detected malicious activity across their networks all of the time by cyber criminals and foreign countries.

Australian Associated Press