Due to the broadcast nature of the wireless medium, wireless networks are highly susceptible to jamming attacks. Such attacks are often studied in a game theoretic framework under the assumption of uninterrupted traffic subject to continuous jamming opportunities. Instead, we analyze the effect of dynamically changing traffic on jamming games for power controlled medium access. Random packet arrivals raise the possibility that the transmitter queues may be empty when jamming attacks start and thus waste the energy of jammers. We consider a non-cooperative game in which transmitters and jammers select their transmission power to balance the transmission cost subject to delay and energy constraints. We show that jammers incur a significant performance loss when they do not have knowledge of transmitter queue states. Dynamic traffic increases the immunity to jamming attacks and gives insights into defense mechanisms.