Turkcell: Tackling CLI spoofing scams through industry collaboration

CLI Spoofing refers to the manipulation of caller line identification (CLI), or caller ID, to falsify the originating phone number displayed on a customer’s phone screen. Scammers operating in another part of the world use this technique to disguise their own identity, while attempting to appear credible by calling from a local number, often a mobile number from the same country as the target customer.

Solution

Turkcell led an innovative joint initiative to tackle overseas CLI Spoofing with Türk Telekom and Vodafone Türkiye, with the support of BTK (Information and Communication Technologies Authority of Türkiye). Under this initiative, mobile network operators query the roaming status of the originating caller through BTKCLI application, based on which the operator decides whether to continue or terminate the call. If the customer is abroad and BTKCLI verifies that their mobile number is roaming on another network, the operator treats the call as legitimate and allows it to reach the recipient. However, if the caller’s mobile is not roaming and the network traffic originates from a foreign network, the operator identifies this as CLI spoofing and blocks the call, stopping the scam before it reaches the intended victim.

This initiative is an example of the power of mobile network operators working together to protect their customers from scams and is a great improvement on the earlier capability of providing protection to customers only when the spoofed CLI and the target victim numbers were on the same network.

Impact

Turkcell blocked approximately four million calls in December 2025 and estimates this number will increase to approximately 10 million across all operators. It has become clear that collaboration is far more effective than attempting to combat scam calls alone. In the previous model, where each operator could protect only its own subscribers, we were unable to address the broader fraud ecosystem. This demonstrated that a collaborative approach is the key to tackling scam calls comprehensively

Additional information

Cost: The teams incurred only in-house development costs and completed the entire process without additional expenses.

Participating organisations: Turkcell, Türk Telekom, Vodafone Türkiye, BTK (Information and Communication Technologies Authority of Türkiye).

Location: Europe