Ad-hoc Networks are one of the most important achievements of current technology; they can provide communication without needing a fixed infrastructure, which makes them suitable for communication in disaster areas or when quick deployment is needed. However, since this kind of network uses the wireless medium for communication, it is susceptible to malicious exploitation at different layers. One of these attacks is a kind of denial of service attack (DoS) that interferes with the radio transmission channel, this is also known as a jamming attack. In this kind of attack, an attacker emits a radio signal that disturbs the energy of the packets causing many errors in the packet currently being transmitted. Another version of this attack is to constantly emit random semi-valid packets to keep the medium busy all the time, preventing the honest nodes from switching from the listening mode to the transmitting mode. In rough environments where there is constant traffic, a jamming attack causes serious problems; therefore measures to prevent this attack are required. The purpose of this thesis is to explore the underlying principles of jamming attacks (i.e., the effects of modulation techniques, interarrival times of packets, transmitter's and jammer's power) using Opnet® as the simulation tool. This work will be helpful so that in future research a useful, practical and effective solution can be created to countermeasure the effects of jamming attacks. The objective here is to understand, modify, and employ the models in OPNET 12.0® to simulate jamming attacks and understand the limitations of the available models
