No second-wave ransomware cyber-attack worldwide: experts

After locking down the files on a computer, the ransomware called "WannaCry" displays a window demanding the user to pay an initial ransom of 300 U.S. dollars' worth of Bitcoin to regain control of their computer.

The massive cyber-attack, which has affected computers in most of the countries around the world, has also taken its toll in China.

Computers linked to China's education, transportation, public security and petrol sectors have been affected.

Wang Wenyi is an engineer with China's National Computer Virus Emergency Response Center.

Despite the disruption the attack might cause, he says bending to the demands of the hackers is not a good idea.

"If we pay the ransom, then we are risking getting our personal information, including our account information, recorded and stolen. When such information gets into hacker's hand, you might be targeted by a second attack," he says.

White House Homeland Security adviser Tom Bossert says investigators are now trying to back track the source of the attack.

"As of this morning, it has reached approximately 150 countries and infected more than 300,000 machines. The good news is that infection rates have slowed over the weekend. Despite appearing to be criminal activity intended to raise money, it appears that less than 70,000 dollars has been paid in ransoms and we are not aware of payments that have led to any data recovery," he says.

The United States was one of the countries whose federal government systems were not affected by the attack.

Countries such as China, Russia, Germany, UK and others were not as lucky.

Computers across the UK's Health Services sector were locked up in the initial attack on Friday, creating patient chaos across the system.

British Health Secretary, Jeremy Hunt, says fears of a second wave of infections have so far not materialized.

"According to our latest intelligence, we have not seen a second wave of attacks and the level of criminal activity is at the lower end of the range that we had anticipated, and so I think that is encouraging. Although we have never seen anything on this scale when it comes to ransomware attacks, they are relatively common and there are things that you can do, that everyone can do, all of us can do, to protect ourselves against them," he adds.

On Sunday, Microsoft slammed the U.S. National Security Agency (NSA), saying the vulnerabilities used for the attack was first discovered by the spy agency, but it chose to keep them secret until they were stolen and leaked.