Paying ransom money to unlock files encrypted by the global cyberattack does not work, the White House has said.

Homeland security adviser Tom Bossett told reporters he is not aware of a case where transferring $300 (£232) in Bitcoin - the amount demanded from victims of last week's attack - has "led to any data recovery".

President Trump's administration estimates that less than $70,000 (£54,285) has been paid to the criminals behind the ransomware so far.

During a White House briefing, Mr Bossert said no federal systems in the US had been affected by the malicious software, known as WannaCry.

He told reporters that he had spoken with his British counterparts, who said they now had a "feeling of control" after the attack struck 47 NHS organisations.


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Approximately 150 countries have been affected by the cyberattack - and although 300,000 machines were hit, the rate of infection is believed to be slowing down.

After factories, banks, transport systems and government agencies were paralysed by the ransomware, investigators are now trying to close in on the perpetrators.

Security experts are monitoring the Bitcoin accounts used to collect the ransom payments. Although the account holders can remain anonymous, clues can often emerge when the money is converted back into real-world currency.

In its latest update on the cyberattack, Europol said it was the "largest ransomware attack observed in history".

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Russia has denied it had anything to do with the cyberattack, with President Vladimir Putin describing it as payback for the US intelligence services.

His remarks came after Microsoft's chief legal officer Brad Smith said the US National Security Agency had developed the original code used in the attack, which was later leaked in a document dump.

Mr Putin said during a trip to Beijing: "A genie let out of a bottle of this kind, especially created by secret services, can then cause damage to its authors and creators."

Sky News has learned that health trusts in England were sent details of a security patch last month that would have allowed them to protect themselves.

A spokesman for NHS Digital said: "Our understanding is that if that had been acted on it would have prevented (the malware attack)."

NHS trusts told about security patch last month

Microsoft said the attack was a "wake-up call" and identified "nation-state action and organised criminal action" as "the two most serious forms of cybersecurity threats in the world today".

The company said it had released a security update back in March to protect Windows system computers against such attacks, but said many computers "remained unpatched globally".