Many alert system devices used by radio and TV stations to alert the public of emergencies are susceptible to cyberattacks, security researchers say.

Such cyberattacks could be dangerous if they caused a widespread panic among people, they said.

Security consultancy firm IOActive issued the warning after hackers broke into several television stations' Emergency Alert Systems this week and broadcast warnings of zombies "rising from their graves" and "attacking the living," CNET reported Thursday.

Although in this case it was meant as a humorous hoax, IOActive said, the next cyberattack could claim something like an anthrax attack or terrorist attack and cause a true panic.

Alert devices used by TV and radio stations to air emergency alerts have critical vulnerabilities that make them susceptible to cyberattacks, IOActive researchers said, wherein hackers could create false alerts broadcasts to millions.

"We found some devices directly connected to the Internet and we think that it's possible that hackers are currently exploiting some of these vulnerabilities or some other flaws," Chief Technology Officer Cesar Cerrudo told Computerworld.

At least two types of Emergency Alert System devices are especially vulnerable to attacks, IOActive said, but added the manufacturers were working to fix the issues.