Well considering they're meant to be quite an overwhelming force, there are no real efficient ways to take them head on.
You would rather be looking for an isolated unit and adhere to hit 'n run tactics, whether that may be a mugging, kidnapping or killing of the unit it applies universally. Other then that you won't stand much of a chance opposing them realistically.
Their anonimity protects them a lot from more conventional tactics such as extortion and blackmailing.
So in essence, there's not many way where you could effectively "fuck with them" as they're not there to fuck around so to speak.