The network was created by Korean priests inspired by the underground railway. The secret passages that relaxed African Americans used to flee to free states from the late 1700s to the American Civil War.
The attacks "have become more intense recently," said Ji Seong-ho, a defector and president of Nu Action and Unity for Human Rights (NAUH), a group working to improve human rights in North Korea. "There seem to be five to seven arrests each month. Refugees flee in a group, so up to 20-30 people are arrested each month," Ji said.
Due to the secret care of everything about North Korea, CNN cannot independently verify the numbers.
Most North Koreans flying across the northern border to China are trying to reach South Korea to find a better life away from a regime that controls all aspects of their lives.
China, a closely associated with Pyongyang, does not consider North Korean defective refugees, but sees them as illegal economic migrants. According to a border agreement with North Korea, it is abolished with power.
In a statement given to CNN, a spokesman for the Foreign Ministry of China repeated the country's long-standing policy that North Korea, which is entering China illegally for economic reasons, is not refugees.
The statement added that "China is sticking to the principles and attitudes that combine domestic international laws and humanitarian spirits" when dealing with Norwegians illegally entering China.
] The high stakes risks that come with being caught mean that the active activists and rescuers work extremely carefully to get defects from China and the underground Net is secret.
Although arrests of defects are not new, several activists say it is becoming more common.
"This year, it was very rare for the fugitives to be caught in the safe house," said YH Kim, President of North Korea's Refugee Human Rights Association Korea. China has "ramped up their crashes," he said.
Ji said arrests used to occur in certain regions, but "now it is everywhere in China."
In April, seven North Korean defects, including a 1
In a statement to CNN, an official from the South Korean Foreign Ministry Affairs said the country's government has made "diplomatic efforts" to prevent North Korean refugees from being forced to repatriate "and go wherever they want."
Previously, the deficiencies crossed the Gobi Desert in Mongolia in order to reach the South Korean embassy in the capital Ulaanbaatar. But that route ended in 2010 when Ulaanbaatar reintroduced strong diplomatic relations with North Korea.
& # 39; Growing Anxiety & # 39; in North Korea
Ji, whose group NAUH claims to have helped rescue 60 refugees this year, said the North Korean leader Kim Jong Un summit and US President Donald Trump, who ended without agreement, could be partly behind the crash .
"After the Hanoi summit failed, the North Korean government was tense," Ji said. "There is an increased agitation among North Korean residents."
Within the country, Ji said the market activity was strangled and the distribution became harder.
"Part of it is the sanctions," he said. "Another is money transfer to North Korea from defective outside being blocked. It's done to control the people, but the money was also the source of energy to ease the market."
As negotiations between North Korea and the US stable, the ties between North Korea and China look up.
"From last year, through the summit with Xi, the relationship between North Korea and China was getting closer. It suggests that China is more likely to cooperate with North Korea," said Cheong Seong-chang, Vice President of Research Planning at Sejong Institute.
But tighter relations with China signal bad news for escape.
"Earlier, when the relationship between China and North Korea became closer, the crash intensified. And when they are distant, the breakdown also escapes," Cheong said.
Xi visits Pyongyang
 On Thursday, Xi arrived in Pyongyang for his first official trip to North Korea since coming to power in 2012 – and the first visit of a Chinese leader for 14 years.
Kang Cheol-hwan, director of the North Korea Strategic Center, said high-level visits between the two countries often speak of strengthening security at their common border.
"Every time Kim Jong Un visits China, he asks them to help maintain his regime by securing the border. The Chinese government is dissatisfied with North Korea, it uses the limit as leverage. Xi's visit to the Pyongyang signals (a) strengthened the crash, "Kang said.
After Kim Jong Un came to power in 2011, border security was tightened to avoid the bad mention of errors and prevent information about North Korea trickling into the country, according to Peters, the American priest. An electric stack was added, as well as border cameras, he said.
"On the Chinese side, patrols were also increased because Beijing is afraid that an influx of refugees could destabilize its own regime," Peters recently told CNN.
Activists say the effects of sanctions and the fallout from the failed summit are heading to North Korean citizens who are increasingly hearing more about the outside world through illegal DVDs or USB sticks smuggled into the country or via foreign radio .
Kang said he believes that the number of North Koreans wishing to escape has increased ", but the actual number had fallen due to completing the lock down the border."
"On the border, the Chinese authorities had hung security cameras everywhere and fenced in the length. It's not easy." For North Koreans dreaming of a better life, the already dangerous journey to escape is now more dangerous than ever.