If your org's approved architecture is based on Zero Trust and you use Teams, here is a nifty chart from Microsoft which lays out your plan. If you store any type of controlled data in your tenant, anywhere, you will fall into the Specialized Security Category.

learn.microsoft.com/en-us/securi...

If you see your handle now says “Invalid handle” please reverify it by navigating to Settings > Change my handle > Type in your current handle > Save.
(Basically, update to the same handle.)'

Credits: u/Demand_101 (reddit)