Deep neural networks (DNNs) have achieved tremendous success in many remote
sensing (RS) applications, in which DNNs are vulnerable to adversarial
perturbations. Unfortunately, current adversarial defense approaches in RS
studies usually suffer from performance fluctuation and unnecessary re-training
costs due to the need for prior knowledge of the adversarial perturbations
among RS data. To circumvent these challenges, we propose a universal
adversarial defense approach in RS imagery (UAD-RS) using pre-trained diffusion
models to defend the common DNNs against multiple unknown adversarial attacks.
Specifically, the generative diffusion models are first pre-trained on
different RS datasets to learn generalized representations in various data
domains. After that, a universal adversarial purification framework is
developed using the forward and reverse process of the pre-trained diffusion
models to purify the perturbations from adversarial samples. Furthermore, an
adaptive noise level selection (ANLS) mechanism is built to capture the optimal
noise level of the diffusion model that can achieve the best purification
results closest to the clean samples according to their Frechet Inception
Distance (FID) in deep feature space. As a result, only a single pre-trained
diffusion model is needed for the universal purification of adversarial samples
on each dataset, which significantly alleviates the re-training efforts and
maintains high performance without prior knowledge of the adversarial
perturbations. Experiments on four heterogeneous RS datasets regarding scene
classification and semantic segmentation verify that UAD-RS outperforms
state-of-the-art adversarial purification approaches with a universal defense
against seven commonly existing adversarial perturbations. Codes and the
pre-trained models are available online (https://github.com/EricYu97/UAD-RS).Comment: Added the GitHub link to the abstrac