Identifying and Treating Small Brown or Black Dots in a Log Home Near Frederick, MD

The log home I recently moved into near Frederick, MD, was built in 1986 and the original roof needs replacement. I’m not certain that the problem I’m writing about–small brown or black dots proliferating on window sills and other surfaces–is directly related to the condition of the roof. The spots, or dots, are easily rubbed off. Varnish? At first I thought they were from insects, but a pest inspector said probably not. The most baffling thing is that some of the spots are not in a direct l