High schooler who pledged loyalty to ISIS and learned bomb-making raises 'homegrown radicalization' fears

A suspect in their 20s who pledged loyalty to the Islamic State militant group and attempted to join it as a combatant has been indicted while in detention.

The North Chungcheong Provincial Police Agency's Industrial Technology Security Investigation Unit said Monday it had referred the suspect, identified only as A, to prosecutors on charges of violating the Counterterrorism Act. Police applied Article 17 of the law, which penalizes preparation and conspiracy to join a terrorist organization.

According to police, A spent years gathering information about ISIS on the dark web — hidden corners of the internet — starting in high school. The suspect later accessed ISIS-affiliated websites, pledged allegiance to the group and was preparing to leave the country to enlist as a terrorist combatant when police made the arrest. Investigators found that A had also learned bomb-making and other terrorist techniques during this period.

The investigation revealed that A harbored deep hostility toward Western nations and a specific religion. Police believe the suspect developed extremist tendencies over a prolonged period of exposure to ISIS propaganda. A was reportedly uncooperative throughout the investigation.

The case has drawn attention for exhibiting the hallmarks of "homegrown radicalization" — a process in which an individual drifts into extremism without direct outside recruitment. Police believe A voluntarily converted, then embraced scriptural interpretations that justify armed struggle and terrorism, before attempting to join ISIS.

"Existing counterterrorism frameworks have focused primarily on blocking external threats," an official said. "There is a need to think about how to respond to Korean nationals who radicalize on their own and attempt to join extremist organizations."

According to the North Chungcheong police, this is the first time a Korean national has been referred to prosecutors for attempting to join a terrorist organization since the Counterterrorism Act was enacted in 2016.

A is also believed to have communicated and conspired via SNS with another suspect, identified as B — a university student of similar age who faces comparable charges. B was sentenced in September at the Cheongju District Court to a maximum of one year and six months in prison and a minimum of one year after being charged with accessing ISIS-related websites thousands of times and posting pledges of allegiance to the group while still in high school.

Police launched the investigation after receiving intelligence from the US Federal Bureau of Investigation in early 2025 and have continued the probe for more than a year.