South Korea's defense authorities have raised the cybersecurity alert level by one notch amid reports of fast-spreading ransomware that may be linked to North Korea, an official said Tuesday.

Many networks worldwide have been disrupted by the "WannaCry" malware. Some security researchers say the North may be behind the cyber assault.

(Yonhap-ESTsecurity)
The Joint Chiefs of Staff has already elevated the stage of "INFOCON," an information-related defense alert system, to Level 3 from Level 4, the official said.

He added there has been no damage to the military's computers and networks with regard to WannaCry.

The five-stage INFOCON is meant for vigilance against North Korea's cyberattacks.

More cybersecurity agents are deployed at each heightened INFOCON stage. (Yonhap)