strange white bumps on wall

[Mitchell Litam]

Does anyone know what this is? How to fix it? What may have caused it so I can address it?

As said before it is the staircase on the first floor leading up into the main area.

It is on the porch area and is an exterior wall. What I mean by this is if you were to punch a hole into the wall you would be hitting the exterior wood siding. I didnt really know how else to explain it.

Help?