If your computer was running an old version of Microsoft Windows, chances are, you could be staring at a message saying "pay up to get your data back."
The virus WannaCry 2.0 has already infected hundreds of thousands of computers in more than 150 countries. It encrypts a computer's files and then demands a ransom to recover the locked data.
Qin Hao, a network security specialist from Cheetah Mobile, says there is no solution that will protect you once and for all. What it takes is consistent efforts.
He says anti-virus companies will keep providing their customers with defense products, and hackers will always try to find system bugs and break through the defenses. The confrontation will last. So the best way out is to use the latest defense system and keep it updated.
Zhou Hongyi, the chief of China's biggest Internet security company 360, agrees. He believes there is no perfect anti-virus software. He says cyber-attacks are difficult to defend against because there are always vulnerabilities. What we need to do when we are under attack is to speak out instead of covering it. Individuals, enterprises, and governments need to let professional teams analyze and help solve problems.
According to Xinhua News Agency, about 18,000 IP addresses in China were confirmed to be infected with the virus. Universities and other educational institutions were among the hardest hit. China's cyberspace authority warned computer users to install and upgrade security software to avoid infection.
WannaCry is just one of over 100 different strains of ransomware viruses currently active on the Internet. It wouldn't have been so destructive if it didn't use a cyber-attack weapon, called "Eternal Blue", stolen from the National Security Agency in the US.
Zhou says ransom viruses are nothing new, we have had mature methods to deal with it. But what made WannaCry so devastating is that it had some extra help from Eternal Blue. It's like an ordinary bomb got loaded onto an intercontinental rocket. Zhou stresses that it's lucky that Eternal Blue was only used as ransomware, and did not use the virus to conduct serious crimes like national-level espionage.
Right now, nobody knows who was behind the attack.