If you run an older version of Windows that is no longer supported by Microsoft, you will be vulnerable to WannaCry, according to Microsoft's blog.

'The United States, more than probably any other country, is extremely careful with their processes about how they handle any vulnerabilities that they're aware of, ' Tom Bossert, the White House homeland security adviser, said at a press briefing on Monday.

Some 47 NHS trusts fell victim to these ransomware attacks resulting in devastating consequences for some patients, as operations were cancelled and medical records held for ransom.

In response, Microsoft released a critical security update on Friday for users operating outdated Windows' systems, such as Windows XP, Server 2003 and Windows 8. It forced the closure of multiple hospitals and ambulance companies, among other services and institutions.

How did the attack spread worldwide? Microsoft said then that the dumping of purported National Security Agency spying tools would not affect up-to-date users of Windows. Some even failed to make basic upgrades that might make it tougher for hackers to burrow inside their computer networks.

Like a physiological virus, "WannaCry" uses each infected computer as a host to find another within the same network. Speaking to IndiaTV, IT minister Ravi Shankar Prasad said yesterday that India's cyber security infrastructure was robust and there had been a minimal impact of the attack on India.

Apple is not invulnerable to ransomware attacks, "a common misconception", one expert tells CNBC.

More news: Bank of England keeps rates at record low as economy slows

So far, the culprits are unknown, as is the motivation.

The cyberattack has affected 150 countries and locked 200,000 computers.

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?

On March 14, the company had released a security update to patch the vulnerability.

Kaspersky said it was seeking to develop a decryption tool "as soon as possible". The WannaCry attack is particularly powerful because it doesn't necessarily require users to click a link or download software to spread. It gives incentives to hackers and pays for future attacks. After seven days without a payment, the malware threatens that "you won't be able to recover your files forever".

Tempting as it may be in order to resolve your crisis quickly, law enforcement and cybersecurity experts don't recommend paying the ransom.