See my reply to mjolk. I am under the impression that the "fortress" infrastructure is provided by ctf365.
-----------------Network-----------------------------------
my_fortress <- targeted by: competitors_command&control_box
my_command&control_box :targets -> competitors_fortress
-----------------------------------------------------------
No shady traffic ever needs to traverse the public internet. Only ssh access to my_command&control_box and my_fortress is required. This has the added benefit of normalizing the attacking horsepower of the entrants.