Last week, an alert was issued on a handful of U.S. TV stations warning on an impending zombie attack. Cyber security experts are stating that this is more than a puckish hacker prank, but that the incident exposes lax security practices in a critical public safety system, Reuters reports.

Broadcasters say that poor password security paved the way for the hack, security experts say the equipment use by the Emergency Alert System remains vulnerable while stations allow it to be accessed through the public Internet.

The main fear is that hackers could prevent the government from sending public warnings during an actual emergency, or that malicious actors could conduct a more damaging hoax than an oncoming “zombie apocalypse,” Reuters reports.

Following the attacks, broadcasters were ordered to change the passwords on the equipment used to deliver emergency broadcasts. Several broadcasters stated that they believe the hackers were able to get in because TV stations had failed to change the default passwords used when the equipment is first shipped out from the manufacturer, according to the article.