15/05/2017 9:11 AM AEST | Updated 15/05/2017 1:20 PM AEST

Cyber Attack: What You Need To Know Today

Read this before you go through your emails.

Krisztian Bocsi/Bloomberg
The WannaCry

CANBERRA -- Hopefully it isn't too late, but be especially careful when you turn your computer on this morning.

There's a worldwide extortion plot in the form of a computer virus called "WannaCry".

Australia, according to the Prime Minister's special adviser on cyber security, Alastair MacGibbon, has missed the worst of the "WannaCry" virus - a massive global cyber "ransom" attack affecting 150 countries and hundreds of thousands of users - but he is expecting more Australian victims to turn up on Monday.

"We have seen several impacts, but with respect to small businesses," Prime Minister Malcolm Turnbull updated reporters in Sydney.

"But it is (an) early stage and I am staying in constant contact with my Cyber Security Adviser.

"At this stage we have not seen the impact we have seen for example in the United Kingdom."

WannaCry has hit 200,000 victims in 150 countries over the weekend. It has hit Telefonica in Spain, FedEx in the U.S and the National Health Service in the UK.

Cyber attack: What should you do?

Do not click on emails from unknown senders

Patch or update your operating system

Look to force this action, if you do not see a prompt

Back up your data onto a USB or disk

Visit the Australian Cyber Security Centre (ACSC) website

Contact ACSC if infected

It's not a new type of crime, but MacGibbon said WannaCry is a "particularly bad one". The latest virus exploits a flaw in Microsoft Windows first identified by U.S. intelligence.

The attack involves a malware, known as "ransomware", which locks computers and holds users' files for $300 ransom in bitcoin to retrieve files.

Computing giant Microsoft said the attack should be treated around the world as a "wake-up call", saying software vulnerabilities hoarded by governments have caused "widespread damage".

At least one Australian company appears to have been targeted by the attacks and several others are under investigation.

"We think we have missed the worst of this, which is fantastic," MacGibbon told RN Breakfast on Monday. "But we can never be complacent.

"Then first thing people should be doing (before checking email) when they got to their office this morning is updating their operating system, the Windows operating system, because that is the only thing that is going to protect them against this."

Businesses are being urged by the Turnbull Government to visit the Australian Cyber Security Centre (ACSC) website at or call 1300 292371 (1300 CYBER1).

Any business with an infected system should contact ACSC.

The spread of this ransomware is not currently known, by MacGibbon said it was most likely by email.

"That then means we have got to be careful opening emails from people we don't know," he said.

"Particularly careful clicking on links or opening attachments like a photo or a file."

MacGibbon said Australian authorities are "desperately" working with overseas partners to find the source of the attack. He said it could spread a number of ways.

"We know, of course, that these things can start with what is called 'spear fishing' email attacks," he said. "That is essentially a criminal sending you an email, you either open an attachment or clink on a link."

"It could well be what we call a 'watering hole' attack which is when you go to a trusted website, and a certain type of people go there, certain types of businesses go there, and they download this malicious software just by visiting."

This type of ransomware also has a worm like feature which allows it to "ping" the internet once established so it can seek out other vulnerable systems.

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