The physical layer security (PLS) of reconfigurable intelligent surfaces (RIS) is critical for providing secure and reliable communications in the 6th-generation (6G) wireless systems. This paper contributes to a debate on many aspects of unique vulnerabilities that can arise in the PLS of RIS with malicious attacks on signal processing (SP) in 6G networks. We address and categorize future security threats in RIS-aided networks considering PLS aspects. Metasurface manipulation attacks (MSMA) are based on manipulating metasurface behavior for malicious purposes. In this study, we present the potential hostile activities of MSMA considering the impact of electromagnetic and time-frequency deterioration. In addition, we evaluate various interference-based MSMA and eavesdropping booster-based MSMA (EaB-MSMA), which are novel potential PLS attacks that involve manipulating phase shifting activity with SP on malicious RIS. We also compare performance degradation in the presence of hostile interference-based MSMA through the manipulation of maliciously configured RIS. Additionally, in the EaB-MSMA case, the loss of secrecy capacity is shown to be considerably greater in passive eavesdropping scenarios.