This thesis explores the combined subjects of keep alive forwarding, denial of service attacks and decentralized congestion control. In a society where the technical requirements on vehicles constantly escalate; inter-vehicle communication has risen as a potential springboard for new technologies. The ETSI ITS-G5 standard is a vehicular ad-hoc network standard that offers manufacturers the possibility to include a feature called keep alive forwarding. This feature lets the nodes forward messages on a pre-defined time interval even if the original broadcaster is no longer present. As this feature might provide exploits for potential people with malicious intent it has been evaluated how resilient the standard might be in such a situation. Also included in this thesis is the decentralized congestion control, a feature required by the standard. To evaluate these features a series of simulations has been performed where vehicles in a highway scenario have been exposed to a denial of service attack where the attacker uses the keep-alive forwarding as an exploit. The findings are that decentralized congestion control does mitigate some of the direct consequences of such an attack. Although it does not eliminate these entirely and new problems are introduced. Finally, alternative methods to perform keep alive forwarding are suggested to enhance this feature.