It depends on who is doing the tracking and who the dissidents are. I think most will agree it’s in the interest of the country to track “dissidents” who are bent on inciting “race” wars and so on. Violent anarchists probably also get in that list. Basically any seriously credible threat to the state and its citizens.
In many aspects yes but you also don’t want surprises. Most members of those groups haven’t been caught doing criminal activity; does that mean you ignore them because they haven’t struck.
If you hear rumblings about a heist it makes sense to monitor the conspirators even if they have not yet done the heist.