New Zealanders are saying they've been hit by the cyber attack that's wreaking havoc around the globe.

The government's Computer Emergency Response Team (CERT) said in a message on Twitter this afternoon that it had received a "small number of unconfirmed reports" that the ransomware attack as affecting New Zealanders.

Officials and experts on Sunday urged organisations and companies to update their operating systems immediately to ensure they aren't vulnerable to a second, more powerful version of the malicious software. The cyber attack paralysed computers that run Britain's hospital network, Germany's national railway and scores of other companies and government agencies worldwide.

The attack, already believed to be the biggest online extortion scheme ever recorded, is an "escalating threat" after hitting 200,000 victims across the world since Friday, according to the head of Europol, Europe's policing agency.


"The numbers are still going up," he said. "We've seen that the slowdown of the infection rate over Friday night, after a temporary fix around it, has now been overcome by a second variation the criminals have released."

His concerns were echoed by James Clapper, former director of national intelligence under President Barack Obama. In an interview on ABC's "This Week," Clapper said the worry was "this ransomware attack will be even larger" as people return to their desks after the weekend.

The 200,000 victims included more than 100,000 organisations, Europol spokesman Jan Op Gen Oorth told The Associated Press. He said it was too early to say who was behind the onslaught and what their motivation was, aside from the obvious demand for money.

So far, he said, not many people have paid the ransom demanded by the malware.

The attack held users hostage by freezing their computers, encrypting their data and demanding money through online bitcoin payment - US$300 ($437) at first, rising to US$600 ($875) before it destroys files hours later.

The effects were felt across the globe, with Britain's National Health Service, Russia's Interior Ministry and companies including Spain's Telefonica, FedEx Corp. in the U.S. and French carmaker Renault all reporting disruptions.

Chinese media reported Sunday that students at several universities were hit, blocking access to their thesis papers and dissertation presentations.

Had it not been for a young British cybersecurity researcher's accidental discovery of a so-called "kill switch," the malicious software likely would have spread much farther and faster.

We could potentially see copycats mimic the delivery or exploit method they used.

The 22-year-old researcher known as "MalwareTech," who wanted to remain anonymous, said he spotted a hidden web address in the "WannaCry" code and made it official by registering its domain name. That move, which cost just $10.69, redirected the attacks to the server of Kryptos Logic, the security company where he works. The server operates as a "sinkhole" to collect information about malware - and in Friday's case kept the malware from escaping.

While that quick thinking may have slowed the outbreak, MalwareTech said he was now looking into a possible second wave of attacks.

"It's quite an easy change to make, to bypass the way we stopped it," he told the AP.

Darien Huss, a 28-year-old research engineer who helped MalwareTech, agreed the threat was far from over.

"We could potentially see copycats mimic the delivery or exploit method they used," he said.

Both joined security officials in urging organizations to protect themselves by installing security fixes right away, running antivirus software and backing up data elsewhere.

"Just patch their systems as soon as possible," MalwareTech said. "It won't be too late as long as they're not infected. It should just be a case of making sure installing updates is enabled, installing the updates, and reboot."

The ransomware appeared to exploit a vulnerability in Microsoft Windows that was purportedly identified by the U.S. National Security Agency for its own intelligence-gathering purposes. The NSA tools were stolen by hackers and dumped on the internet.

Experts say this vulnerability has been understood among experts for months, yet too many groups failed to take it seriously. Microsoft had "patched," or fixed it, in updates of recent versions of Windows since March, but many users did not apply the software fix.

Worse, the malware was able to create so much chaos because it was designed to self-replicate like a virus, spreading quickly once inside university, business and government networks.

Microsoft was quick to change its policy, announcing free security patches to fix this vulnerability in the older Windows systems still used by millions of individuals and smaller businesses. Before Friday's attack, Microsoft had made fixes for older systems, such as 2001's Windows XP, available only to those who paid extra for extended technical support.

"The problem is the larger organisations are still running on old, no longer supported operating systems," said Lawrence Abrams, a New York-based blogger who runs "So they no longer get the security updates they should be."

Short of paying, options for those already infected are usually limited to recovering data files from a backup, if available, or living without them.

British cybersecurity expert Graham Cluley doesn't want to blame the NSA for the attack.

"There are other criminals who've launched this attack, and they are ultimately responsible for this," he said. "But there's clearly some culpability on the part of the U.S. intelligence services. Because they could have done something ages ago to get this problem fixed, and they didn't do it."

He said most people "are living an online life," and these agencies have a duty to protect their countries' citizens in that realm as well.

"Obviously, they want those tools in order to spy on people of interest, on other countries, to conduct surveillance," Cluley said. "It's a handy thing to have, but it's a dangerous thing to have. Because they can be used against you. And that's what's happening right now."

How, exactly, does this ransomware work?

As its name implies, ransomware works like a hostage-taker.

Once your computer is infected, the attack can do a couple of things. One common approach: Your files will be encrypted or converted into a different language for which only the hacker has the cipher. Often, you won't even know you've been targeted until you try to open a file.

Another, more damaging version is what happened Friday: The ransomware locks you out of your entire system.

During the attack in England, computer screens showed a message demanding $300 in bitcoin in exchange for the decryption key that would unlock the files.

Victims had three days to pay before the fee was doubled. (Something very similar happened to a hospital system in Los Angeles a couple of months ago.

The hospital ended up paying about $17,000. The hackers even set up a help line to answer questions about paying the ransom.)

This attack relies on something called the Wanna Decryptor, also known as WannaCry or WCRY.

These kinds of attacks are particularly hard to spot, especially because hackers are always tweaking them. The Wanna Decryptor being used is just weeks old, and it was just updated.

How do computers get infected?

Lots of ways.

Hackers can get ransomware on your system if you download an infected piece of software or a PDF. They can also use a phishing email to direct you to an infected website.

In this case, hackers sent a zip file attachment in an email. When victims clicked on it, their computers were infected. But the attack didn't stop there. The ransomware spread through the hospitals' and businesses' computer networks. "Once you get a foothold in the system, other users will start to run those pieces of software," explained Clifford Neuman, who directs the University of Southern California's Center for Computer Systems Security.

What can I do to stay safe?

First, back up your hard drive. You should be keeping frequent backups anyway, in case your computer dies on its own. But if your computer gets hacked, you'll be able to retrieve your data without paying a ransom.

If you run a business, back up every computer in your office and have a plan for what to do if your system goes down for a while. Be smart about setting up your network, so that most users don't have complete access to the system.

This makes it harder for a ransomware attack to infect everything. And make sure your users are educated about the common kinds of attacks.

Avi Rubin, a Johns Hopkins professor who studies computer hacking, has one other piece of advice: If you or your business get attacked, don't pay.

"You're funding the bad guys and giving more incentive," he said. You also don't know whether your files will really be restored.