  Recent astrophysical observations have motivated novel theoretical models of
the dark matter sector. A class of such models predicts the existence of GeV
scale cosmic strings that communicate with the standard model sector by
Aharonov-Bohm interactions with electrically charged particles. We discuss the
cosmology of these "dark strings" and investigate possible observational
signatures. More elaborate dark sector models are argued to contain hybrid
topological defects that may also have observational signatures.
