In wireless sensor networks (WSNs), as the shared nature of the wireless medium, jamming attacks can be easily launched and result in a great damage to the network. How to deal with jamming attacks has become a great concern recently. Finding the location of a jammer is important to take security actions against the jammer, and thus to restore the network communication. After a comprehensive study on the jammer localization problem, a lightweight easy-operated algorithm called triple circles localization (TCL) is proposed. The evaluation results have demonstrated that, compared with other approaches, TCL achieves the best jammer localization accuracy under variable conditions. In wireless sensor networks (WSNs), as the shared nature of the wireless medium, jamming attacks can be readily launched and result in a great damage to the network. How to deal with jamming attacks has become a great concern recently. Finding the location of a jammer is important to take security actions against the jammer, and thus to restore the network communication. After a comprehensive study on the jammer localization problem, a lightweight easy-operated algorithm called triple circles localization (TCL) is proposed. said that compared with other approaches, TCL achieves the best jammer localization accuracy under variable conditions.