Image-Synthesis-Based Backdoor Attack Approach for Face Classification Task

Although deep neural networks (DNNs) are applied in various fields owing to their remarkable performance, recent studies have indicated that DNN models are vulnerable to backdoor attacks. Backdoored images were generated by adding a backdoor trigger in original training images, which activated the backdoor attack. However, most of the previously used attack methods are noticeable, not natural to the human eye, and easily detected by certain defense methods. Accordingly, we propose an image-synthesis-based backdoor attack, which is a novel approach to avoid this type of attack. To overcome the aforementioned limitations, we set a conditional facial region such as the hair, eyes, or mouth as a trigger and modified that region using an image synthesis technique that replaced the region of original image with the region of target image. Consequently, we achieved an attack success rate of up to 88.37% using 20% of the synthesized backdoored images injected in the training dataset while maintaining the model accuracy for clean images. Moreover, we analyzed the advantages of the proposed approach through image transformation, visualization of activation regions for DNN models, and human tests. In addition to its applicability in both label flipping and clean-label attack scenarios, the proposed method can be utilized as an attack approach to threaten security in the face classification task.