The recent bust of a suspected spy ring based in Cheongju, North Chungcheong Province, raises concerns that not a few espionage agents may be lurking in South Korean society and working to benefit North Korea.

The authorities on Monday detained three of four activists who had organized protests opposing the purchase of F-35A stealth fighters from the US. They were charged under the National Security Act. They allegedly took orders from Pyongyang when they staged street gatherings and a series of single-person relay protests.

The National Intelligence Service and police reportedly found that the activists had formed an underground “North Chungcheong Comrade Party for Independent Unification” with the goal of subverting the South Korean system. They are said to have spied on military units and used their personal connections with the ruling Democratic Party of Korea and former leaders of the Korean Confederation of Trade Unions to carry out espionage operations, involve some 60 regional politicians and activists in a campaign against the introduction of the stealth fighters, and inculcate North Korea’s ideology in young people, including unionists and irregular workers in the province. Evidence of this was found on a USB flash drive seized at the home of a suspect. Oaths of allegiance to North Korean leader Kim Jong-un were found too, written in the suspects’ own blood.

They allegedly contacted North Korean intel officers in China and Cambodia and received $20,000 from them to fund espionage.

They publicly supported Moon Jae-in, then a presidential candidate, as part of a special advisory body on labor issues for his campaign in 2017. One of the four suspects, who was an executive member of the KCTU, ran in Daejeon in 2016 as an independent candidate for a National Assembly seat.

Another suspect, who ran an internet news organization, ran for chair of the North Chungcheong committee of a legitimate far-left political party last year. The suspect ran for provincial city councilor in 2014 and worked at a think tank affiliated with Ahn Cheol-soo, then a lawmaker, in November 2013. Disguised as regional labor activists, the three allegedly tried to influence politics.

They reportedly met with an unidentified senior lawmaker from the ruling party and proposed creating inter-Korean businesses.

If spies following North Korean orders penetrate into political parties or government agencies, policies on North Korea will likely be distorted, endangering national security.

The investigating authorities should reveal the full picture of the espionage scandal. People cannot but wonder how the suspects became part of a presidential campaign organization, how they were able to meet with a senior lawmaker, and how many allies they gained.

The government slashed its budget for the purchase of the F-35As this year and last year, reallocating the funds for COVID-19 relief. In this connection, a question arises. Was it wholly accidental that the budget was curtailed specifically for F-35A fighters, out of all the weapons South Korea was set to purchase? The North fears the stealth fighters.

Under the Moon regime, often criticized for being too submissive to North Korea, it is rare to hear news of arrests on charges of spying for North Korea. The administration effectively has taken no issue with anti-American and pro-North Korean protests and rallies. An alliance of pro-North Korean university students formed a committee that praised North Korean leader Kim Jong-un and held an event in Seoul inviting him to visit South Korea.

A civic group representing the victims of Japan’s wartime sexual slavery, once chaired by Rep. Yoon Mi-hyang, is suspected of misusing money donated for the funeral of a former comfort woman by giving it to those who opposed the deployment of US missile defense systems in South Korea and those who sought to repatriate women who had escaped from North Korea.

The government must reflect on whether it unwittingly fostered an atmosphere conducive to secret activities benefiting North Korea.

Probably the alleged spy ring is just part of a larger force that cries for peace outwardly while working for North Korea behind the scenes. The authorities must root out spies acting to subvert the South Korean system under the cloak of labor or civic activism. That is the way to protect our hard-won free democracy.