ForensicsForest Family: A Series of Multi-Scale Hierarchical Cascade Forests for Detecting GAN-Generated Faces

The prominent progress in generative models has significantly improved the authenticity of generated faces, raising serious concerns in society. To combat GAN-generated faces, many countermeasures based on Convolutional Neural Networks (CNNs) have been spawned due to their strong learning capabilities. In this paper, we rethink this problem and explore a new approach based on forest models instead of CNNs. Concretely, we describe a simple and effective forest-based method set, termed ForensicsForest Family, to detect GAN-generate faces. The ForensicsForest family is composed of three variants: ForensicsForest, Hybrid ForensicsForest and Divide-and-Conquer ForensicsForest. ForenscisForest is a novel Multi-scale Hierarchical Cascade Forest that takes appearance, frequency, and biological features as input, hierarchically cascades different levels of features for authenticity prediction, and employs a multi-scale ensemble scheme to consider different levels of information comprehensively for further performance improvement. Building upon ForensicsForest, we create Hybrid ForensicsForest, an extended version that integrates the CNN layers into models, to further enhance the efficacy of augmented features. Furthermore, to reduce memory usage during training, we introduce Divide-and-Conquer ForensicsForest, which can construct a forest model using only a portion of training samplings. In the training stage, we train several candidate forest models using the subsets of training samples. Then, a ForensicsForest is assembled by selecting suitable components from these candidate forest models. Our method is validated on state-of-the-art GAN-generated face datasets and compared with several CNN models, demonstrating the surprising effectiveness of our method in detecting GAN-generated faces.