Poland: emergency radio signals spoofed, halting trains

Between 25 and 29 August 2023, unknown actors transmitted the unencrypted "radio-stop" emergency signal on Polish railway radio frequencies, triggering automatic emergency braking and halting trains in several parts of the country. The first incidents struck the Szczecin area in the north-west on 25 August, with further disruptions reported near Gdynia, Białystok and elsewhere in the following days. Roughly 20 passenger and freight trains were brought to a standstill, causing hours of delays before services resumed. No injuries were reported.

The radio-stop function works by broadcasting three audio tones over the analogue railway radio network, which is neither encrypted nor authenticated; the necessary equipment is cheap and widely available, making the signal trivial to spoof. In some cases the stop signals were reportedly interspersed with recordings of the Russian national anthem and excerpts of speeches by Vladimir Putin. Poland's Internal Security Agency (ABW), police and rail operators launched an investigation, with officials publicly raising the possibility of Russian-linked destabilisation given Poland's role as a transit hub for Western arms to Ukraine. Two Polish citizens, aged 24 and 29, were detained in Białystok, where investigators seized radio equipment; one suspect was reported to be a serving police officer.

The incident demonstrated how a decades-old, unencrypted railway radio standard can be disrupted with inexpensive, off-the-shelf equipment, requiring little technical sophistication. The injected Russian anthem and Putin audio, combined with Poland's importance to Ukraine-bound logistics, fuelled suspicion of a Russian-linked operation, and Polish officials framed it within broader destabilisation efforts. However, the detained suspects were Polish nationals and a definitive foreign-state link was not publicly established; the affair is best characterised as suspected sabotage under investigation. The episode accelerated plans to migrate Polish railways to encrypted, authenticated GSM-R radio.