UK regulator launches inquiry on mobile spoofing

Ofcom, the UK telecoms regulator, has issued a Call for Input (CFI) to address mobile spoofing. The CFI requests feedback on technical solutions under discussion. Let’s have a look.

The problem: spoofing of mobile calling numbers

Ofcom has already mandated rules to prevent fraudsters from harming consumers with spoofed calls. The rules require operators to:

  • Block calls with calling numbers on a DNO (Do Not Originate) list
  • Block calls from abroad that spoof a UK fixed network number
  • Exercise due diligence when allocating numbers to other UK operators.

These rules allow operators to accept calls from abroad with Calling Line Identification (CLI) of a UK mobile number.

Fraudsters are exploiting this loophole by spoofing UK mobile numbers on their scam robocalls to consumers in the UK.

Potential solutions

The CFI identifies two proposed solutions:

  1. Roaming check: The UK-based international gateway provider would check with the home mobile network for the calling number to determine whether the number matches a phone which is currently roaming abroad.
    • If the home provider response confirms that the number is roaming, then the international gateway provider routes the call to its destination, else it may block the call.
  2. Home Routing: The international gateway provider removes or withholds the CLIs and routes calls from abroad with mobile CLIs to the caller’s home network rather than directly to the called party.
    • The home network provider would check whether the number is registered as roaming and either restore the CLI and route the call to the called party.
    • There are options for call handling if the home network cannot be identified or the number is not roaming. The call might be blocked, or it could be routed for termination without a CLI or with the CLI withheld.

More information

Responses are due September 23, 2024.

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