If the government is in control of the network or can can order / request the network to do so it would be fairly trivial to send a message to anyone connected

If the government is in control of the network or can can order / request the network to do so it would be fairly trivial to send a message to anyone connected to a cell tower. The thing is if the tower is serving a lot of people you could end up sending the message to people not involved so you could use a IMSI catcher (you can even make them out of a TV Tuner turned SDR receiver[0]) to catch IMSI's in a smaller area or use triangulation to narrow down the pool of devices in an area and then use that list to send SMS from the network itself. The UK did trails of using location based text messages back in 2013 in order to be used for Public emergency alerts [1] When you can gain access to the network their is no real need to MITM it, but yeah I believe a sting ray type device could also do the same as they act as a tower and trick your phone into connecting to it. [0] https://github.com/Oros42/IMSI-catcher https://github.com/Oros42/IMSI-catcher [1] https://www.gov.uk/government/publications/mobile-alerting-trials-for-public-emergencies https://www.gov.uk/government/publications/mobile-alerting-t... (link to the info about the trial and the final report)