'Accidental hero' triggers 'kill switch' to halt spread of ransomware behind NHS cyber attack

More than 70 countries are thought to have been affected by the ransomware bug Credit: Alex Milan Tracy/SIPA USA/PA Images

An "accidental hero" has halted the spread of the malware virus that caused chaos in the NHS and around the world simply by registering a website domain, according to reports.

A 22-year-old UK cybersecurity researcher known online as MalwareTech, together with researcher Darien Huss from security firm Proofpoint, are credited with finding the "kill switch".

The researchers spotted a long domain name made up of a series of apparently random letters in the malware code and purchased the site, not realising at the time that the move would stop the virus.

Purchase of the domain reportedly cost $10.69 (£8.30), marking a relatively cheap way to put an end to a virus thought to have hit companies and organisations in more than 70 countries.

"I saw it [the site] wasn’t registered and thought, 'I think I’ll have that,'" MalwareTech is reported by The Daily Beast as saying.

The virus, known as WannaCrypt or variations of that name and which utilises a tool developed by the NSA, appears to search the internet for a web address which stops the worm's transmission once activated.

When the site registration was detected by the virus it stopped its worldwide spread.

Connections to the domain have now been "sinkholed" to a server in California.