  The existence of shocks driven by Coronal Mass Ejections (CMEs) has always
been assumed based on the superalfvenic speeds for some of these events and on
indirect evidence such as radio bursts and distant streamer deflections.
However, the direct signature of the plasma enhancement at the shock front has
escaped detection until recently. Since 2003, work on LASCO observations has
shown that CME-driven shocks can be detected by white light coronagraph
observations from a few solar radii to at least 20 Rsun. Shock properties, such
as the density compression ratio and their direction can be extracted from the
data. We review this work here and demonstrate how to recognize the various
shock morphologies in the images.We also discuss how the two-viewpoint
coronagraph observations from the STEREO mission allow the reconstruction of
the 3D envelope of the shock revealing some interesting properties of the
shocks (e.g., anisotropic expansion).
