Prime Minister Malcolm Turnbull stood by his decision to stand with the UK in its defiance of the nerve agent attack in Salisbury, and slammed Russia's use of cyber tactics against the west.

"The message has to be sent by nations in solidarity that this type of illegal conduct whether it is a chemical attack in Syria, the use of a nerve agent on British soil or the expanding cyber attacks across the internet across the whole digital domain on which all of our businesses and economies depend. These must be resisted. They must be detected. They must be identified and we must do everything we can to make our countries, our citizens secure again," the Australian prime minister said.

UK Prime Minister Theresa May praised the work of the Five Eyes alliance in tracing February's NotPetya attack to Russia, but cautioned more acts of cyber warfare are likely and nations must be prepared for these attacks.

"Russia is using cyber... they’re using cyber as part of a wider effort to attack and undermine the international system," Prime Minister May said.

"And its interference over the past year has included attacks on public sector, media, telecommunications and energy sectors. And co-operation between our nations allowed us to trace February's NotPetya attack to Russia."

"I've been clear to Russia that we know what it is doing and we should be in no doubt that such cyber-warfare is one of the greatest challenges of our time and working with our closest allies, three of whom are here today. We will work around the clock with all the technology at our disposal to stop aggressive states and non-state actors from succeeding."

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Canada's Prime Minister Justin Trudeau said the threats of cyber attacks will continue to grow as the world becomes more digitalised.

"We recognise the arrival of new threats as we get more and more digital, as we develop AI, as we look at new technologies and ways of empowering citizens and enhancing their lives, we also have to be aware of the vulnerabilities that come with it," Prime Minister Trudeau said.

"There is a potential slide towards more strong arm tactics of more authoritarian governments that we've seen elsewhere around the world so the importance of like-minded friends and partners, like us four, to stand together, to be aware of these challenges and mostly to work together to provide a response and a solidarity, that is a clear message to those around the world who do not play by the same rules."

New Zealand's Prime Minister Jacinda Ardern also spoke of the shared security challenges the Five Eyes alliance is facing.

"There is no doubt we broadly face common security challenges, challenges that do not respect borders or boundaries and we all benefit from a collective rules-based approach," Prime Minister Ardern said.

The comments from the four prime ministers come after the US, Britain and Australia alleged Russian government-backed hackers infected computer routers across the globe in a cyber espionage campaign that targeted government agencies, businesses and critical infrastructure operators. 

Australia's Minister for Defence Marise Payne said up to 400 Australian businesses may have been targeted in the attacks.