Wildlife Spotting

you have a point there Scott, there are 7-9 leaves, R. canina is mostly growing 5-7 leaves. :)

The terminal leaflets look a little too long and pointy, but your description of its aggressive growth, and the small, white, notched petals all suggest the dreaded Rosa multiflora. Are the bases of the leaves fringed? http://plants.usda.gov/java/profile?symbol=ROMU

that´s definitely a wild rose (could be a Rosa canina I think)