Whatever Does Not Kill Deep Reinforcement Learning, Makes It Stronger
  Recent developments have established the vulnerability of deep Reinforcement
Learning (RL) to policy manipulation attacks via adversarial perturbations. In
this paper, we investigate the robustness and resilience of deep RL to
training-time and test-time attacks. Through experimental results, we
demonstrate that under noncontiguous training-time attacks, Deep Q-Network
(DQN) agents can recover and adapt to the adversarial conditions by reactively
adjusting the policy. Our results also show that policies learned under
adversarial perturbations are more robust to test-time attacks. Furthermore, we
compare the performance of $\epsilon$-greedy and parameter-space noise
exploration methods in terms of robustness and resilience against adversarial
perturbations.
