SINGAPORE - All incoming international calls from Wednesday (April 15) will be prefixed with a plus sign (+), in an effort to combat spoof calls from overseas and better protect the public from scams.

The authorities hope that this measure, which was announced last month, will help consumers who are not expecting any overseas calls to be more vigilant and careful when answering calls that show this prefix.

For instance, if an overseas caller tries to spoof a local mobile phone number, the number will appear as +91234567.

Calls from Singapore will not display such a sign.

The Info-communications Media Development Authority (IMDA) has been working with telecommunications companies here to make sure that all network users have access to the function by Wednesday.

According to the Singapore Police Force's annual crime brief for last year, more than $21 million was reported lost to impersonation scams, where callers pretended to represent organisations like banks or insurance companies to fool victims into transferring them money.

These scammers hide their original country code and are able to make their phone numbers appear like local numbers on a potential victim's caller ID.

In order to combat these scams, the Government formed an Inter-Ministry Committee on Scams to jointly tackle this problem.

When introducing this method of detection during the debate on the budget of the Ministry of Communications and Information (MCI), the Senior Minister of State for Communications and Information Janil Puthucheary noted that international scammers are known to impersonate local phone numbers.

He added that the IMDA currently already works with telcos to block commonly spoofed numbers such as 999 or 995.

"We hope this will help consumers better identify international spoof calls and reject them," he had said then.