The WannaCry virus, the name of the ransomware used for the cyber attack, does not affect other systems, such as Apple.
It said the ransomware called "WannaCry" or "WannaCrypt" encrypts the computer's hard-disk drive and then spreads laterally between computers on the same local area network (LAN).
"It has been reported that a new ransomware named Wannacry is spreading widely. This is because if one computer (which, along with 50 other computers are part of the same internet connection), gets infected by the ransomware, all the other computers could get infected and all the data could be lost", Mukesh said.
The scale of the attack prompted Microsoft to take the highly unusual step of releasing patches for unsupported operating systems, including Windows XP.
"The WannaCrypt exploits used in the attack were drawn from the exploits stolen from the National Security Agency, or NSA, in the United States", the company added.
Organizations are scrambling to apply the latest security patch to their computers to prevent the spread of the attack.
The anonymous specialist, known only as MalwareTech, issued a warning that hackers could upgrade the virus to remove the kill switch. However, the latter version is non-functional and seems to have been a test by someone who manually patched the binary to remove the kill switch, rather than recompiling it from its original source code. A "patch" is a piece of software created to update a computer program or its supporting data, to fix or improve it. But that's complicated, because hackers need to find security flaws that are unknown, widespread and relatively easy to exploit.
Monday could bring a wave of attacks to the U.S., warned Caleb Barlow, vice president of threat intelligence for IBM.
"In the meantime, we wish to reassure patients that your GP will be there for you as usual if you are taken ill and that you will receive the best possible care from the NHS, despite the current difficulties". But millions of individuals and smaller businesses still had such systems.
The recent global cyber attack has affected more than 200,000 people - so should you be anxious about your own online security? To some extent, this is understandable because deploying patches in environments with a large number of systems is not an easy task. And those fixes will do nothing for newer systems if they aren't installed.
The Kaspersky Lab estimated up to five percent of computers affected around the world could be located in India, due to the number of computers there using older versions of Microsoft's operating system. Companies including Hitachi and Nissan Motor Co. reported problems but said they said had not seriously affected their business operations.
Among those affected by the virus was Nissan UK, but the auto manufacturer said there had been no major impact. "In those cases, it's imperative they properly understand the risks and look into workarounds to limit the threat".
At least one strain of the ransomware has proven especially vicious.
The cyber attack was expertly hidden but a vigilant young scientist along with fellow 20-something engineers was able to detect and stop it. In a scathing statement over the weekend, he said an equivalent scenario in conventional weapons would be the USA military having some of its Tomahawk missiles stolen.
"But let me just assure you, we are spending money on strengthening the cyber defence of our hospital system". The healthcare centres in many countries are particularly vulnerable.