An adversarial sample detection method based on heterogeneous denoising

Deep learning has been used in many computer-vision-based applications. However, deep neural networks are vulnerable to adversarial examples that have been crafted specifically to fool a system while being imperceptible to humans. In this paper, we propose a detection defense method based on heterogeneous denoising on foreground and background (HDFB). Since an image region that dominates to the output classification is usually sensitive to adversarial perturbations, HDFB focuses defense on the foreground region rather than the whole image. First, HDFB uses class activation map to segment examples into foreground and background regions. Second, the foreground and background are encoded to square patches. Third, the encoded foreground is zoomed in and out and is denoised in two scales. Subsequently, the encoded background is denoised once using bilateral filtering. After that, the denoised foreground and background patches are decoded. Finally, the decoded foreground and background are stitched together as a denoised sample for classification. If the classifications of the denoised and input images are different, the input image is detected as an adversarial example. The comparison experiments are implemented on CIFAR-10 and MiniImageNet. The average detection rate (DR) against white-box attacks on the test sets of the two datasets is 86.4%. The average DR against black-box attacks on MiniImageNet is 88.4%. The experimental results suggest that HDFB shows high performance on adversarial examples and is robust against white-box and black-box adversarial attacks. However, HDFB is insecure if its defense parameters are exposed to attackers.