The brown marmorated is an invasive species – introduced from Asia – and is now found all over the mid-Atlantic region.
Most stinkbugs, including the brown marmorated, are plant feeders, and can be serious agricultural pests if numerous enough. Stinkbugs are named for the glands which release an unpleasant smelling ooze when the insect is disturbed. My advice – don’t disturb them!
Want to learn more about the brown marmorated? Penn State’s entomology department is at your service – http://ento.psu.edu/extension/factsheets/brown-marmorated-stink-bug.