A 23-year-old university student in Taiwan was arrested for interfering with the TETRA communication system used by the country's high-speed railway network (THSR). According to local media reports, the student halted four trains for 48 minutes on April 5 by using software-defined radio (SDR) communications and handheld radios to transmit a high-priority “General Alarm” signal, triggering emergency braking procedures. THSR is a high-speed railway network in Taiwan that runs a single 350 km (217 miles) two-way line along the western coast of the country, with trains reaching speeds of up to 300 km/h (186 mph). The annual ridership is 81.8 million passengers, making it a crucial service that also receives financial support from the state. Before the attack, the student, who is referred to by his surname Lin, intercepted and decoded TETRA (Trans-European Trunked Radio) radio parameters using SDR equipment he bought online, and then programmed them into handheld radios to impersonate legitimate beacons. The police also found that a 21-year-old accomplice provided Lin with some critical THSR parameters that enabled the attack. Reports state that the system had been in use for 19 years and that its parameters were apparently not rotated during that time, allowing the hacker to bypass seven verification layers. The incident has sparked criticism from some Taiwanese politicians, who called out the bodies responsible for negligence.