Old hat, actually:
Someone calls and says they are from Microsoft and would help you clean your PC. In reality, remote maintenance is set up, the criminal counterpart encrypts your PC and thus wants to extort a “ransom”.
BWI currently operates two chat solutions for the Bundeswehr for official and private mobile devices: Matrix and stashcat.
https://www.bwi.de/news-blog/news/artikel/kommunikation-in-covid-19-zeiten-bundeswehr-setzt-instant-messaging-ein
…
In the course of further expansion, Matrix will replace stashcat as the federal armed forces' standardised instant messaging platform.
