In a multihop ad hoc network, end-to-end data transmissions traverse through multiple inter-node wireless links. A jammer can disrupt the entire data transfer of a network by intentionally interfering with links between a subset of nodes. The impact of such attacks is escalated when the jammer is moving. While the majority of current ad hoc protocols consider omnidirectional transmission and reception, adaptive antennas can be utilized for spatial filtering of the jamming signal. This paper investigates the performance of employing adaptive beam nulling as a mitigation technique against jamming attacks in multihop ad hoc networks. Considering a moving jammer, the survivability of links and connectivity in such networks are studied by simulating various node distributions and different mobility patterns of the attacker. In addition, the impact of errors in estimation of direction of arrival and beamforming on the overall network performance are also examined. The results indicate a significant improvement in retaining connectivity under jamming when adaptive beam nulling is applied.