Call ID spoofing: How to protect yourself from fraudulent calls

Online criminals pretend to be police officers or bank employees and call with fake numbers. This is how this call ID spoofing works and how to protect yourself from scammers.

Organized crime has been operating a lucrative business model with call centers, many of which are located in Turkey, for years. They usually call older people and pretend, for example, that they are police officers or employees of a bank. The called party often sees an unsuspicious phone number on the display of their landline or mobile phone. In particularly brazen cases, the emergency number for the police (110) appears on the display.

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Cyber ​​criminals use call ID spoofing

In this way, the perpetrators want to trick their victims into handing them cash, jewelry and other valuables or to transfer larger sums of money. The illegal call ID spoofing, the transmission of a wrong number, should make the calls appear even more convincing. The call then appears to come from the local area network of the called party or from a service number (e.g. 01805- or 0800-). Sometimes the phone numbers don’t even exist – sometimes the area code is already invalid. A callback after a missed call then goes nowhere.

The callers are often in a call center abroad, for example in Turkey. They use the services of dubious VoIP providers (Voice-over-IP, Internet telephony), with which they can specify the phone numbers they want to transmit to the person they are calling. These VoIP service providers are often based overseas, for example in Tonga. German telecommunications companies (network operators) cannot check caller numbers (caller IDs) transmitted from abroad.

How to protect yourself from scammers on the phone

The best protection comes without any technical aids: common sense. The police would never call you to take custody of your valuables or cash. Your bank would never call you to transfer large amounts to an unknown account under time pressure. If a caller asks you to do something of this nature, on whatever pretext, hang up immediately. Forget your cultivated politeness – it won’t get you anywhere here.

Use the blocking list of the Fritzbox

If you operate your telephone (e.g. a DECT telephone) on a Fritzbox with an integrated telephone system, you can feed the integrated blocking list. Calls from numbers stored in it are no longer put through, so the phone does not ring. However, the blocking list can quickly fill up because it only has 32 entries. If you frequently receive unsolicited advertising calls, create a second phone book in the Fritzbox in which you can store phone numbers to be blocked. How to set up this number blocking, we explain in this guide.

Fritz box call list

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Tellows call protection for Fritzbox

However, this protection against unwanted calls only works afterwards, so it only protects against repeated calls from the same number. The company Tellows offers current lists of already known spam phone numbers as a (paid) subscription, which you can import into the Fritzbox. We explain how this works in this guide.

Buy Tellows call protection for the Fritzbox

Do not disturb for the smartphone

You can also protect yourself against unwanted calls on your mobile phone within certain limits. For example, Tellows offers the “Caller ID & Blocker” app for Android and iOS in a free basic version and an ad-free Pro version. Numerous other apps offer similar functions, often with SMS blocking.

Call Blocker Apps on Google Play

Call ID spoofing can also be used for legitimate purposes

If you find a call in the call list of your Fritzbox for which a second number is given in brackets after the number shown on the display, the call is coming from a connection in Germany or in a country with a similarly strictly regulated telephone network. In addition to the user-defined number, the exchange also transmits the actual number of the telephone connection. here


there is a halfway legitimate use of call ID spoofing, for example if a company wants to transmit a different telephone number (such as that of the head office or a call center) for any callbacks – instead of the extension number of the employee calling.

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