Jamming attacks, as a form of a denial-of-service attack, significantly degrade the performance of wireless communication systems and can lead to significant overhead in terms of re-transmissions and increased power consumption. In this work, we demonstrate the optimal jamming waveform in internet-of-things (IoT) networks. In particular, we present the analytical bit error rate (BER) of the system under attack by employing two common jamming waveforms: Gaussian noise, and digitally modulated. Then, we validate this analysis with the aid of simulations using the MATLAB WLAN toolbox. Obtained analytical and simulation results, demonstrated system performance degradation under jamming attacks. The simulation results agree with the analytical results in terms of determining the effective jamming waveform. Furthermore, the simulation results depict a 100% PER when the jamming to signal ratio (JSR) is OdB for both QPSK modulated and Gaussian noise waveforms which corroborates with the findings in the literature.