We investigate the instabilities of a linear damped oscillator due to fluctuations of the damping parameter. The
fluctuations are driven either by Gaussian white noise or Poisson white noise (white shot noise). We consider
three notions of stability. The first two are the well-known notions of stability in the mean and stability in the
mean square. We introduce the concept of thermodynamic stability, corresponding to a nonpositive rate of energy
dissipation at all times. We derive analytical results for the various instability thresholds, confirm the validity of
our approach for white shot noise by numerical simulations, and obtain the unexpected result that mean-square
and thermodynamic stability coincide for the two types of white noise.