I guess it's a protection, look at this picture, on the same place as where the tapes are, there are two round things (dunno the use, maybe something to mesure air pressure for the flight instrumen, that's just a guess)
The rings are just paint showing where the static port is. The actual static port is about the size of a quarter. In storage and during longer maintance checks they are covered to protect them and to keep them from getting clogged.
Those static ports are called Gust Supression ports. There are 4 ports (2 on each side). These ports measure differential pressure on both sides of the vertical stabilizer.
These inputs are to detect yaw rate. This system does essentially the same thing as a Yaw Damper, but the B777 doesn't have a system called Yaw Damper. It's called Gust Supression, but it does the same thing (aid in roll control and improves pax comfort).