These types of systems are typically radio controlled, and their reference to working with the FCC (regulator of radio transmissions) makes it pretty clear that the vector here was via radio.<p>The control system is usually very simple - newer systems might use FSK digital signalling or even 900MHz spread spectrum, but a lot of siren systems out in the field right now are controlled by DTMF over business band radio, usually using the same frequency as the mobile radios of whatever department installed the system, just to avoid the overhead of getting a new license.<p>So it's likely that someone here just worked out what frequency the siren controllers listen on and what protocol they use, both of which could be done pretty easily just by going through frequencies the municipal government has licenses for and trying common manufacturer's commands, using a typical commercial radio (or anything they could get to transmit in those bands - e.g. firmware hacked amateur equipment, SDRs, etc). There are lots of ways to take informed guesses at these parameters too, e.g. manufacturer labels on the control cabinets might reveal what protocol is in use.<p>Just taking a wild guess from licenses in the area, Dallas's sirens might be controlled off of the city's POCSAG paging system. It looks like it has solid coverage and Federal Signal (major siren manufacturer) makes a POCSAG-capable controllers. POCSAG is an FSK digital protocol, there's open source software to implement it. Since Dallas conducts regular tests it would be a simple thing to monitor their POCSAG frequency during the test and see if you receive any pages to special numbers.<p>As far as catching the crooks... well, the FCC has an enforcement division, but it is well known to be small and largely powerless these days when it comes to local radio issues. Just because of the physical difficulty of radio direction finding and monitoring a large country, the FCC probably won't be able to do a thing unless the offenders make a habit of it, allowing someone to bring in radio direction finding equipment and catch them in the act.<p>The complete lack of security in many radio-controlled systems is a real concern. Other areas you find highly exploitable radio control schemes include various kinds of industrial automation and infrastructure systems. A trivial example people might be inclined to casually hack on, besides municipal sirens, would be irrigation. A lot of golf courses have a DTMF-over-handheld-radio control facility for their irrigation to aid groundskeepers in maintenance. Particularly easy to get a hold of since there's only a couple of manufacturers of these systems and most golf courses will only have a license for one business band frequency.
All my dallas friends (used to live there) were posting about waking up to this. Those things are frikkin loud if you are close to them. Let alone the annoyance I'm sure this was a distraction to first responders , hope nobody got hurt.
I would love to hear the technical details on this one... Systems like these tend to be so old and unmaintained, I can't understand why it would need to be hooked up to the network instead of being a big red button in an office somewhere and learning how it was owned might let me work that bit out :)