Polish Rail Traffic Interrupted by Intentional Radio Interference
"dalek" writes:
Gizmodo and Wired, among other sources, report that Polish railways were halted on Friday and Saturday due to unauthorized radio broadcasts. Polish railroads use the broadcasting of three tones on the 151.010 MHz frequency to instruct trains to stop. This occurred in three locations around Poland. Cheap radio equipment would be sufficient to issue the stop command, though it required that whoever broadcasted the signal would need to be in close proximity to the location affected. Despite the simplicity of the attack, there probably needed to be some coordination to broadcast the signals at different places in Poland.
There is no authentication or encryption to issue the emergency stop command, though discussions on various forums suggest that only the stop command is broadcast in this manner. A general design principle in railroad signaling systems is that the default should be to stop trains. For example, the multi-colored signaling lights commonly used in the United States and Canada that still mechanically switch between colors will default to a red stop signal. Trains require long distances to stop, and defaulting to a stop signal will prevent collisions. Authorities in Poland insist that there was there was no safety risk to rail passengers, and this seems reasonable if the unauthorized broadcasts were only able to issue an emergency stop command but not to instruct trains to move.
When this topic was discussed on Slashdot, it quickly turned to politics, but I find the technical aspects of this much more interesting. In North America, lights and semaphores are common and simple signaling mechanisms that have widespread use. For example, I know from experience that the same signaling system described in the video for use in Canada is also used on many BNSF main lines in the United States. However, other systems are also in use like the Advanced Train Control System (ATCS) and Positive Train Control (PTC). At some locations in the US, it was possible to use a software defined radio and software like ATCSMon to track the locations of trains in the area. However, railroads also generally also use unencrypted voice communications between trains and dispatchers, and these can still be monitored with a scanner.
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