About Malicious Phone Calls
The following provides an overview of the various countermeasures that DOCOMO undertakes with regards to the so called "one-ring" call phenomenon in which users are lured into calling back a number in the received call history that connects to a dating agency or adult content provider.
To avoid unexpected trouble, be especially careful with regards to calling (calling back) any phone number that you do not know in your received call history. In particular, if the call destination is overseas, the charge will be for an overseas call and there are cases where it may become high. Please check the number before dialing. For suspicious incoming calls from overseas, refer to Notices about World Calls (Communication Failures, etc.) (in Japanese only).
This service allows you to use your phone worry free by notifying you in advance of incoming calls from numbers thought to be used for persistent sales calls and other nuisance calls or scam calls and other dangerous calls.
Anshin Security (in Japanese only)
Countermeasures for One-Ring Calls
A call from an unknown number that ends after one ring is a "one-ring call". If you call back the number from your received call history, you may be connected to a dating agency or adult content provider that will bill you an outrageous call charge. This page introduces the countermeasures for malicious calls that use such deceptive means.
Countermeasures for One-Ring Calls (in Japanese only)
Countermeasures for Prank Calls, Repeated Wrong Number Calls, and Other Nuisance Calls
This page introduces countermeasure for blocking prank calls and repeated wrong number calls.