The deployment mode that allows an Intrusion Detection System (IDS) or Intrusion Detection and Prevention System (IDPS) to both detect and stop malicious traffic is known as inline mode. In this mode, the IDS/IDPS is placed directly in the network's traffic flow. All traffic must pass through the system, allowing it to inspect packets in real-time and take immediate action to block potential threats before they reach their destination. This contrasts with promiscuous or passive modes, where the system only monitors and alerts on traffic without the ability to intervene directly.