/Courtesy of Twitter

By Lee Han-soo

North Korea resumed its cryptic broadcasts for sleeper agents in South Korea on Friday.

It was the first such broadcast since the North halted the program after the first inter-Korean summit in 2000.

"We will now broadcast the math homework review section for 27th trainee for remote education college," said a female broadcaster after the official broadcast from Pyongyang Broadcasting Station ended at 12:45 a.m.

She went on, saying "Page 459 No. 35, page 913 No. 55, page 135 No. 86."

The broadcast continued the series of five numbers repeatedly for 12 minutes. It is believed to be a code for operatives in the South.

"This is the same MO that the North used before it halted the broadcast after the 2000 inter-Korean summit," said an expert on North Korea.

"North Korea used to broadcast a song praising Kim Il-sung and Kim Jung-il before certain numbers were read repeatedly for 15 minutes."

The expert said the latest cryptic broadcast could be viewed in three ways.

"First it can be viewed as an actual command for operatives in the South as all operatives are assigned a specific number," he said.

"Second, it can be a false broadcast to confuse the information branch in South Korea.

"Finally it may be a broadcast to test their system."

However, experts say it is most likely part of North Korea's psychological warfare because the method is way outdated.

Nowadays North Korea is known to use steganography, which is concealing a file, message, image, or video within another file, message, image, or video.

This was verified during the latest arrest of a North Korean sleeper ring in 2011.