ah, some reportage on the matter

[click picture]
Pictured is the Kabul-Torkham Highway, the vehicle passable section of the northeastern half of the Afghanistan/Pakistan border area, and here is a map that can give you some idea of the general terrain. Nobody in history has been able to overtake the inhabitants of this area successfully. The tribes have it nailed down. You'd have to kill every living thing in the entire area to impose anything like "border security" there... and, short of nukes, good luck on that one, too.

Oh, yeah, here's some border securitizing for ya:

[border guards' shift change]

[supply line for border stations]

[Pashtuns]

[Pashtuns dispensing with border hassles]