The Australian Signals Directorate issued advice for utility providers on Tuesday in a 16-page guide co-signed by Five Eyes intelligence partners in Canada, New Zealand, the UK and US.
The advice follows sophisticated attacks on critical infrastructure by China-sponsored hacking groups, including one that compromised nine US telecommunications companies.
It also comes weeks after Telstra suffered a national telecommunications outage that caused widespread disruption in retail stores, transport, and emergency services.
The agency's paper, called CI Fortify, was developed in conjunction with industry partners and designed to help critical infrastructure providers isolate operating technology from the rest of their network.
Operating technology can include switches, pumps and other equipment that is vital to delivering services such as water and power but is less sophisticated than other parts of a network.
The age, design and basic connectivity of this equipment can leave it vulnerable to online attacks, Australian Signals Directorate Cyber Uplift assistant director general Heidi Hutchison said.
"It's often easier to target, especially since… a lot of the connectivity that has been built into it in the past 10 years or so hasn't necessarily been done with cybersecurity in mind," she told AAP.
"This is asking entities to think more seriously about the architecture that needs to be in place."
The security advice is designed to help essential service providers isolate parts of their network for up to three months to give them time to respond to an online attack.
Recent attacks on critical infrastructure by China-backed hacking groups changed the threat level for utility providers, she said, including Salt Typhoon that pre-positioned itself within water and energy firms, and Volt Typhoon that infiltrated telecommunications companies.
"There was no other reason for an actor to be sitting where they were sitting except to cause disruption to the services — it had no espionage value," Ms Hutchison said.
"That was a real indication that we needed to better prepare our critical infrastructure to be able to identify these actors in their environments."
Advice from the Australian Signals Directorate includes identifying vital systems, networks and customers, building isolation points to contain attacks, and testing isolation plans.
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