Security agencies are hunting for those behind a crippling “ransomware” cyberattack which has so far hit hundreds of thousands of computers worldwide, including at government agencies, factories and health services. Here is what we know so far about the cyber ransom attacks:
What happened?
The cyberattacks started Friday and spread rapidly around the globe using a security flaw in Microsoft's Windows XP operating system, an older version that is no longer given mainstream tech support by the US giant.
The malware, known as “WannaCry”, locks access to user files and in an on-screen message demands payment of $300 in the virtual currency Bitcoin in order to decrypt the files.
Who has been affected?
Europol chief Rob Wainwright said computer systems in more than 150 countries were hit, with the majority of organisations affected over the weekend in Europe.
But as Asia woke up to the working week on Monday, leading Chinese security-software provider Qihoo 360 said "hundreds of thousands" of computers in the country were hit at nearly 30,000 institutions including government agencies.
In Japan, a spokesman for Hitachi said the conglomerate discovered problems on Monday morning and its computer networks were "unstable".
Other high-profile victims include hospitals in Britain, the Spanish telecoms giant Telefonica, French carmaker Renault, US package delivery company FedEx, Russia's interior ministry and the German rail operator Deutsche Bahn.
Where did the malware come from?
Brad Smith, Microsoft's president and chief legal officer, said in a blog post Sunday that the culprits used a code developed by the US National Security Agency.
It was leaked as part of a document dump, according to researchers at the Moscow-based computer security firm Kaspersky Lab.
Who was behind the attack?
Europol's senior spokesman Jan Op Gen Oorth said it was still "a bit early too say who is behind it, but we are working on a decrypting tool".
Experts think it unlikely to have been one person, with criminally minded cyber crime syndicates nowadays going underground and using ever more sophisticated encryption to hide their activities.
How can people protect their computers?
Microsoft took the unusual step of reissuing security patches first made available in March for Windows XP and other older versions of its operating system.
Kaspersky said it was seeking to develop a decryption tool "as soon as possible".
