Reconfigurable intelligent surface (RIS) has been developed as an efficient technology to make the electromagnetic environment programmable by adjusting the passive reflecting elements. Despite its benefits, the RIS may serve as a passive jammer by manipulating the environment when utilized by an adversary. In this paper, we investigate the impact of benign and malicious RISs on multiple-input single-output (MISO) wiretap channels. In particular, we design an efficient joint transmit beamforming and benign RIS phase shifting strategy under the worst-case secrecy rate achieved by optimizing the malicious RIS’s phase shifting strategy. In doing so, we formulate a max-min secrecy rate problem, and propose a suboptimal algorithm based on alternating optimization (AO) with two inner gradient-descent-ascent (GDA) algorithms. Numerical results show that a positive secrecy rate is guaranteed when the benign RIS’s reflecting channel dominates the malicious RIS’s reflecting channel.