a 23-year-old Taiwanese student "hacked" the Taiwan high-speed rail line, bringing four trains to a standstill, because the RF system in use hadn't had its crypto keys rotated in 19 years.

 https://www.tomshardware.com/tech-industry/cyber-security/college-student-hacks-taiwan-high-speed-rail-line-stopping-four-trains-19-years-without-crypto-key-rotation-ends-in-predictable-result