(Newser) – Mysterious radio broadcasts out of North Korea are raising Cold War concerns in South Korea, the AP reports. A woman read a string of meaningless numbers on North Korean state radio for two minutes on June 24. It happened again last Friday; this time for 14 minutes. Popular Mechanics gives an example of what this sounded like: "On page 459, question number 35, on page 913, question number 55, on page 134..." and so forth. The woman on the radio says the numbers are "review assignments in physics" or "practice assignments in mathematic lessons." But what they really sound like are the secret messages North Korea used to send to its spies in South Korea during the Cold War.

While some in South Korea believe North Korea is once again using the radio to pass missions along to its spies, experts aren't so sure. North Korea stopped using this method in 2000 with the advent of the internet and newer, better methods of hiding messages. It would be odd for North Korea to go back to an outdated system that South Korea already knows about. Plus, broadcasting these kinds of messages immediately alerts everyone that you're doing something shady. “If it really is espionage activity, it’s pretty old school," writes Matt Novak at Gizmodo. "But I guess that’s how North Korea operates these days anyway.” Experts think it's possible the strange numbers are just North Korea's attempt at psychological warfare. The country is currently upset with South Korea for hosting a US missile defense system. (It's not that happy with the White House, either.)

