Phone tapping is the act of a third party illegally intercepting the content of a phone call. In Japan, the secrecy of communications is protected under Article 4 of the Telecommunications Business Act, and wiretapping is punishable by up to 3 years' imprisonment or a fine of up to 2 million yen. Article 21, Paragraph 2 of the Constitution also guarantees the secrecy of communications, making it a legally very serious crime.
Tapping methods differ significantly depending on whether the target is a landline or mobile phone. For landlines, physical connection to the phone line (tapping) is the classic method. Bugs are commonly placed on the phone unit itself, modular jacks, or outdoor wiring boxes, and commercially available devices can be purchased for just a few thousand yen, making the technical barrier low. Mobile phone calls, on the other hand, are digitally encrypted (AES encryption from 3G onward), making it extremely difficult to decrypt intercepted radio signals.
However, mobile phone tapping risk is not zero. IMSI catchers (fake base stations, also called Stingrays) impersonate legitimate base stations to connect devices and intercept communications during relay. While law enforcement uses them for investigations, criminal misuse has been reported overseas. Additionally, if spyware is installed on a smartphone, not only call content but also SMS, location data, and camera footage can be monitored.
If tapping is suspected, take a step-by-step approach. For landlines, hire a specialist to sweep for bugs (typically costing 30,000-100,000 yen). For smartphones, check for unfamiliar apps and update the OS to the latest version. For VoIP calls, using end-to-end encrypted services (Signal, WhatsApp, etc.) significantly reduces interception risk along the communication path. In serious cases, consult the police and consider applying the Anti-Stalking Act or Unauthorized Computer Access Act. See Call Recording Legal Guide for the boundary between legal recording and illegal wiretapping.