Osama bin Laden managed to hide in plain sight for 6 years by doing something similar.
The basic approach of senior Al Qaeda figures was to use laptops but never connect them to the internet. Everything was based on thumb drives, which were moved around by trusted couriers. You couldn't plant a mole in there, because they basically didn't trust anyone they hadn't known for several generations.
He was eventually tracked down because his most trusted courier was on the phone with a friend being pestered about what he was doing, and the CIA happened to be listening.