Many phone handsets are equipped with calling number display (“CND”), enabling the called party to see the number of the person calling before he/she answers the call.  The telephone number shown on the CND is, however, susceptible to be changed/falsified by scammers by means of “caller ID spoofing”.  According to the Police, there has been a surge in phone scams lately involving caller ID spoofing.  The Police indicates that these phone scams originate from outside Hong Kong.

 “+” Sign to Indicate Incoming Calls From Outside Hong Kong

To help detect caller ID spoofing, as from 21 August 2015, the telephone operators are required to insert a “+” sign in the CND of mobile phones as a prefix for all incoming calls originating from outside Hong Kong, even if, for instance, the calling number is masqueraded as a local Hong Kong phone number.  The “+” sign enables the public to identify from the CND the origination of the incoming calls is from outside Hong Kong.

Limitations about “+” Sign on the CND

The display of the “+” sign on the CND of a mobile phone for an incoming external call may be subject to the following limitations:

The insertion of the “+” sign to all incoming calls originating from outside Hong Kong seeks but to alert the public to possible phone scams.  Whether or not the “+” sign is shown on the CND of mobile phones, members of the public are advised to always stay vigilant in regard to suspicious phone calls from dubious callers.  In order to avoid falling into the traps of fraudsters who are engaged in caller ID spoofing, you are advised to take the following precautionary measures:

Precautions against Caller ID Spoofing


Office of the Communications Authority


 1  For example, the “+” sign cannot be shown on the CND of certain very aged model phones (such as those which show digits only).