The continuous increase in network attacks and the complexity of the available offensive technologies enforces novel defensive mechanisms. Moving Target Defense (MTD) is a recent family of approaches for network defense. This study proposes MaTaDoR, which utilizes message authentication akin to TCP Authentication Option (TCP-AO) in a MTD setting to mitigate a wide range of attacks, including Denial of Service (DoS). The purpose of MaTaDoR is averting unauthenticated packets from reaching protected assets. When many other MTD approaches aim to delay adversaries, MaTaDoR strictly protects networked assets from unauthenticated access. MaTaDoR is transparent, stateless and scalable. The efficiency of this combination is demonstrated by the results of a simulation. The proposed approach is capable of blocking every DoS packet with an insignificant trade-off increase in end-to-end delay.