Passive attack usually means that the threat actor collects the data without taking an active part. It set the traps, and now he can lean back on the chair and sip his coffee - victims will bring their data themselves. Unfortunately for the crooks, such easy prey is not actual anymore. Passive MITM attacks - generally ones that apply Wi-Fi access point spoofing - was actually in the early ‘00s. Thereat, Wi-Fi protection was weak, and HTTPS was not used, making it possible for attackers to apply no complicated techniques.