Fixed target experiments are a particularly useful tool in the search of very weakly coupled particles in the MeV-GeV range that could explain the baryon asymmetry of the Universe, the nature of the Dark Matter and the origin of the neutrino masses and oscillations. The NA62 experiment at the CERN SPS is currently taking data to measure the rare decay $K^{+}\rightarrow\pi^{+} v \bar v$. Owing to the high beam-energy and high beam intensity, a long decay volume and a hermetic detector coverage, NA62 also has the opportunity to directly search for a plethora of hidden-sector particles, both in visible or invisible final states. We will detail on status and prospects of these searches, with special focus on those that can be performed with the experiment operated in beam-dump mode.