  We revisit the possibility of using cosmological observations to constrain
models that involve interactions between neutrinos and dark matter. We show
that small-scale measurements of the cosmic microwave background with a few per
cent accuracy are critical to uncover unique signatures from models with tiny
couplings that would require a much higher sensitivity at lower multipoles,
such as those probed by the Planck satellite. We analyze the high-multipole
data released by the Atacama Cosmology Telescope, both independently and in
combination with Planck and Baryon Acoustic Oscillation measurements, finding a
compelling preference for a non-vanishing coupling, $\log_{10}u_{\nu
\textrm{DM}}=-5.20^{+1.2}_{-0.74}$ at 68% CL. This aligns with other
CMB-independent probes, such as Lyman-$\alpha$. We illustrate how this coupling
could be accounted for in the presence of dark matter interactions with a
sterile neutrino.
