I am anxious about how the numbers will continue to grow when people go to work and turn on their machines on Monday morning.

British cybersecurity expert Graham Cluley doesn't want to blame the NSA for the attack, though he said they have a duty to citizens who "are living an online life".

But the agency added that some infections may not yet have been detected, and that existing infections can spread within networks.

Organizations around the world spent the weekend trying to recover after being hit by a virus that seeks to seize control of computers until victims pay a ransom.

Friday's attack affected acute hospital sites in Lanarkshire, as well as GP surgeries, dental practices and other primary care centres around the country.

Speaking after a Cobra meeting on Saturday, Home Secretary Amber Rudd admitted "there's always more" that can be done to protect against viruses.

The NHS says it employs more than 1.5 million people, making it one of the world's biggest employers alongside the U.S. Department of Defence, Walmart and the Chinese army.

That was the chilling prediction made yesterday by Ron Wainwright, the English-born head of the EU's crimefighting organisation Europol.

There are different variants of what happens: Other forms of ransomware execute programs that can lock your computer entirely, only showing a message to make payment in order to log in again.

Trump 'shared secret information about IS' with Russian officials
The report notes that Trump disclosed the information to Russian Foreign Minister Sergey Lavrov and Russian Ambassador to the U. House Minority Leader Nancy Pelosi also slammed Trump and called for a briefing.

The virus spread quickly because the culprits used a digital code believed to have been developed by the US National Security Agency - and subsequently leaked as part of a document dump, according to researchers at the Moscow-based computer security firm Kaspersky Lab.

In the wake of the attack, Microsoft said it had taken the "highly unusual step" of releasing a patch for computers running older operating systems including Windows XP, Windows 8 and Windows Server 2003. Windows 10 machines were not subject to the vulnerability this patch addressed and are therefore not at risk of the malware propagating via this vector. "And I think it's going to grow", said former director of National Intelligence, James Clapper in an interview with ABC.

"We are now seeing more than 75,000 detections.in 99 countries", Jakub Kroustek of the security firm Avast said in a blog post. Investigators are working to track down those responsible for the ransomware used on Friday, known as Wanna Decryptor or WannaCry.

Given the attack's widespread nature, even such a small sum would stack up quickly, though few victims seem to be paying up so far.

WannaCry has already caused massive disruption around the globe.

The country most affected by "WannaCry" is said to be the United Kingdom, where 48 of the 248 National Health Service trusts were hit, causing widespread disruption to health services in the country. "You're only safe if you patch ASAP", he wrote on Twitter. Copycat attacks by other high-tech criminals also are possible. Wannacry encrypts the files on infected Windows systems.

"These ransomware attacks have been on the rise over the last three years, it wasn't exactly something that was a shock - what was surprising is the scale of this one".

Germany's rail operator Deutsche Bahn said its station display panels were affected.