Generating network traffic flows remains a critical aspect of developing cyber and network security systems. In this survey, we first consider the history of network traffic generation methods and identify the weaknesses of these. We then proceed to introduce more recent approaches based on machine learning (ML) models. In particular, we focus on Generative Adversarial Network (GAN) models, which have developed from their initial form to encompass many variants in today's ML landscape. The use of GANs for generating traffic flows that have appeared in the literature are then presented. For each instance, we present the architecture, training methods, generated results, identified limitations and prospects for further research. We thus demonstrate that GANs are key to future developments in network traffic generation and secure cyber and network systems.