  Recent years have witnessed the great success of deep learning algorithms in
the geoscience and remote sensing realm. Nevertheless, the security and
robustness of deep learning models deserve special attention when addressing
safety-critical remote sensing tasks. In this paper, we provide a systematic
analysis of backdoor attacks for remote sensing data, where both scene
classification and semantic segmentation tasks are considered. While most of
the existing backdoor attack algorithms rely on visible triggers like squared
patches with well-designed patterns, we propose a novel wavelet transform-based
attack (WABA) method, which can achieve invisible attacks by injecting the
trigger image into the poisoned image in the low-frequency domain. In this way,
the high-frequency information in the trigger image can be filtered out in the
attack, resulting in stealthy data poisoning. Despite its simplicity, the
proposed method can significantly cheat the current state-of-the-art deep
learning models with a high attack success rate. We further analyze how
different trigger images and the hyper-parameters in the wavelet transform
would influence the performance of the proposed method. Extensive experiments
on four benchmark remote sensing datasets demonstrate the effectiveness of the
proposed method for both scene classification and semantic segmentation tasks
and thus highlight the importance of designing advanced backdoor defense
algorithms to address this threat in remote sensing scenarios. The code will be
available online at \url{https://github.com/ndraeger/waba}.
