How to track a fake number

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In order to manipulate a number and to transmit and display a wrong number when calling, it is not necessary to obtain this number in any way, i.e. to acquire it or to have it activated. On the one hand, real existing phone numbers - including foreign ones - can be affected by the manipulation, although the owner of the phone number has nothing to do with the call. On the other hand, fantasy numbers can be used, i.e. phone numbers that have not been assigned and therefore cannot be assigned to anyone.

The purpose of setting up a telephone number is to conceal the true identity of the caller. According to the experience of the Federal Network Agency, calls with falsified sender information have quite different backgrounds - the bandwidth ranges from harmless, so-called "fun calls" to criminally motivated calls, which the law enforcement authorities are responsible for clearing up. Consumers should therefore first contact the responsible police station in the event of a suspicion.

The use of manipulated sender numbers is also referred to under the term "Call ID spoofing" summarized.

Receipt of alleged callbacks: Indication of Call ID spoofing

If real existing phone numbers are set up for calls, it can happen that the real number owner receives supposed callbacks on his connection. This happens e.g. B. when the real existing phone number (illegally) is used as a sender phone number as part of an advertising campaign where z. B. A predictive dialer is used to call a large number of people displaying this number. If the call is not accepted, the number appears in the list of missed calls. If those affected call back, they can reach the actual number owner, even if he has nothing to do with the calls.

If a real existing phone number is extended by one or more digits during the original call, the redundant digits are simply truncated by the system when the extended phone number is called back, with the result that the call still reaches the actual subscriber. When using the callback function, the caller can therefore reach the actual number owner even if the assigned number was extended. Depending on the number of calls placed, the actual subscriber can be significantly impaired by supposed callbacks.

Sender numbers can be fake and cannot be trusted without reservation.

Police emergency number 110

There are no calls for which the emergency number 110 is legitimately displayed as the sender number.

If the emergency number 110 appears as the sender number for a call, its display has been manipulated in any case. The emergency number 110 is used by the police as a dial-in number. H. The police can be reached by citizens via this emergency number. Police emergency call centers, however, never call this number themselves. Rather, the local network numbers of the individual police stations are used for this purpose.

In fact, no calls can be made via the emergency number.

Nevertheless, the Federal Network Agency regularly receives information that consumers are receiving calls using the emergency number 110. The callers pretend to be police officers. According to previous experience, these calls always have a criminal background. As a rule, the perpetrators try to get hold of the victims' money by faking a wide variety of legends.

If you receive a call indicating 110, you should therefore immediately contact the law enforcement authorities, e. B. Contact the local police station.

Options for action

On the one hand, the suspicion of phone number manipulation opens up the scope for action under Section 67 (1) TKG. According to this, the Federal Network Agency can take orders and other suitable measures within the framework of number management to ensure compliance with statutory provisions and the conditions it has issued regarding the allocation of numbers. In particular, the law provides for the order to switch off an illegally used number as a rule in Section 67 (1) sentence 5 TKG. Deactivating a number means that it is no longer technically accessible or can no longer be called from it.

Arranging a shutdown is, however, not a sensible measure with regard to an incorrectly displayed phone number, since the calls are actually made from a different connection. In the continuation of these calls, the deactivation of the phone number that is actually not involved in the calls can change anything. Only a disconnection arrangement would make sense with regard to the call number from which the calls originate, but which is usually unknown and would first have to be determined.

In general, the adoption of measures to prevent calls with manipulated phone number displays is ultimately always linked to the determination of the person responsible.

Enforcement Obstacles

However, the Federal Network Agency is only rarely able to determine who is responsible for identified phone number manipulations: The information from which connection the calls actually came from is a so-called traffic date. In contrast to the law enforcement authorities under the requirements of Section 100g of the Code of Criminal Procedure, the Federal Network Agency has no authority to intervene vis-à-vis the network operators to request information about traffic data. There is a lack of the necessary legal basis to intervene in the secrecy of telecommunications, which is protected by fundamental rights.

The Federal Network Agency can therefore only pursue violations on a regular basis if the relevant information can be obtained in other ways, for example because the person called had an interception circuit installed at the time of the call or B. the router used (e.g. Fritz! Box) has read out the corresponding information. In addition, there may be indications of the perpetrator or other investigative approaches from the content of the telephone conversation.

The identification of perpetrators can be made even more difficult because, according to local knowledge, many cases of call ID spoofing involve foreign countries, be it that the calls are made from there or are routed via foreign networks. In international traffic in particular, the phenomenon can be observed that the original number (the so-called “network provided number”) is falsified or transmitted incompletely. In addition, telecommunications services in Germany are increasingly being offered over IP-based networks, in which the switching equipment is also partly or wholly abroad.

The powers of the Federal Network Agency are limited to the territory of the Federal Republic of Germany. The clarification of abuse with a foreign connection and the prosecution of offenders based abroad or also service providers based there who enable phone number manipulation therefore regularly prove to be difficult.

The assessment and ultimately the decision as to the extent to which administrative authorities are given investigative powers to prosecute abuse are the responsibility of the legislature. So far, the latter has refrained from permitting interference with the secrecy of telecommunications, which is protected by fundamental rights, in order to investigate violations of the corresponding provision in Section 66k TKG. As a state authority, the Federal Network Agency is subject to the constitutionally guaranteed reservation of the law. Action is therefore only possible with express legal authorization; otherwise the authority itself behaves illegally.

In order to continue to improve the protection against telephone number manipulation, the Federal Network Agency depends on the support of citizens by reporting violations

Tips for your protection

Block phone numbers
Some network operators offer their customers the option of blocking entire phone number groups or just individual phone numbers. The respective providers provide information on blocking options.
Depending on the equipment of the end device, the telephone system or the mobile phone, it is also possible to block number in your own device. If necessary, these functions can be set up in the router, the private branch exchange or in the end device itself (including mobile phone). Further information on number blocking by routers, private branch exchanges or end devices can be obtained from specialist dealers or the manufacturer.
Ask for additional "security package"
Some network operators offer paid protection options. In some cases, you can book a so-called "security package" for your contract for a monthly fee. In order to clarify whether such an option is offered by your network operator, you must contact them.

Flying restart: For incoming calls in the future, under certain conditions, you can apply to your subscriber network operator (i.e. your telephone provider to set up a chargeable interception circuit (MCID, English abbreviation for Malicious Call Identification) in order to make the suppressed number visible This means that no calls can be read out later. The subscriber concerned can, however, also subsequently try to obtain information about the connection from his subscriber network operator. However, in view of the legally protected telecommunications secrecy, network operators are not obliged or even not without it The most realistic chance of finding out who is actually responsible for the calls is therefore if such an interception circuit occurs at the time of the call s was already installed.


In certain cases of manipulated telephone numbers, however, it is not even possible to determine from which telephone number the call actually originated from the data of the telephone connection. This is e.g. B. conceivable if the routing, as is often the case, takes place abroad or the call even originates abroad. In such cases, the establishment of the connection is much more difficult for German authorities to understand. In addition, many calls originate in the Internet, which offers a wide range of manipulation options. In fact, it is difficult to elucidate such connections.

No technical prevention options by the Federal Network Agency

The Federal Network Agency has no technical means of preventing calls with manipulated sender information. Rather, the operators of telecommunications law institutions, i.e. the network operators and telecommunications providers, have the sole technical influence. There are also very different statements from there as to whether and in which specific constellations such a technical possibility of prevention currently exists.

Suspected criminal calls

The Federal Network Agency is not responsible for the prosecution and investigation of criminal offenses and, in the absence of jurisdiction, is not authorized to do so. The execution of this task is the sole responsibility of the law enforcement authorities.

The law enforcement authorities are given further investigative powers under the requirements of Section 100g of the Code of Criminal Procedure (StPO). In the case of certain offenses in criminal proceedings, for example, it is possible to query the traffic data. Section 100g of the Code of Criminal Procedure permits this in the case of offenses of considerable importance, in particular in the case of a catalog offense under Section 100a (2) of the Code of Criminal Procedure, or for those that were committed via telecommunications.

Acting quickly can be decisive here. In those cases in which calls with manipulated phone numbers may have a criminal law background, e.g. For example, if a criminal offense is suspected (e.g. telephone fraud) or a preparatory act, the complainants are therefore strongly recommended to contact the law enforcement authorities as soon as possible in order to prevent the loss of data due to the lapse of time. For example, connection data that are not important for billing purposes are only available to the network operators for a short period of time. Billing-relevant data is also deleted within certain deadlines. The first point of contact for those affected can be the local police station.

You can find more protection tips here.

Legal regulations

Rights and obligations in connection with the transmission of telephone numbers are contained in Section 66k TKG.

According to this, providers of telecommunications services must ensure that a nationally significant number is transmitted and identified as such as the caller's number when the connection is established. The number must be assigned to the respective subscriber for this service. Other providers involved in the connection are not allowed to change the transmitted phone number.

This number is the so-called “network provided number”, which should be used to identify the respective caller - for example for billing purposes or in connection with public safety issues (e.g. for emergency calls or surveillance measures).

The respective subscriber may also set up an additional number for the purpose of transmission to the called party and transmit it to the public telephone network (so-called generic number). This takes into account the legitimate interests of call number owners in the use of an additional call number generated by the respective subscriber, for which there are quite sensible possible applications. So z. B. especially in the business sector transparency can be established in this way, for example, if a company or an authority calls via a well-known number established in the market, regardless of which network access or which location the call is set up in the individual case.

The transmission of an additional, subscriber-generated phone number is, however, linked to certain strict requirements. The subscriber must have the right to use the corresponding number. Such rights of use to a number can only be acquired through allocation. An agreement concluded by contract to be able to use the phone number, however, is not sufficient.

The following German special numbers may not be transmitted as a phone number by providers or set up by participants:

  • 118xy (information services)
  • (0) 137 (mass transit services)
  • (0) 12 (Novel Services)
  • (0) 900 (Premium Services)
  • 5- or 6-digit numbers for speed dial voice services

Relationship between section 66k and section 102 (1) and (2) TKG - number suppression

According to section 102 (1) sentence 1 TKG, callers and those called must be able to suppress the caller's number displayed by the service provider permanently or individually for each call in a simple manner and free of charge. If the caller makes use of this option in accordance with section 102 (1) sentence 1 TKG, his phone number will therefore not be displayed to the called party.

The obligation under Section 66k (1) TKG for network-side signaling remains unaffected even in the case of number suppression in accordance with Section 102 (1) TKG: on the network side, the assigned number that sets up the call must always be transmitted. This remains recognizable for security authorities and is also important in the context of billing between the network operators involved in the connection. The display of the signaled phone number is suppressed only for the called party.

The right to suppress the number display according to Section 102 (1) TKG is, however, expressly excluded according to the provision in Section 102 (2) TKG for advertising calls.

More on this.

For all other calls of a private or business nature that do not represent advertising, there is no obligation to display the number to the called party according to the telecommunications regulations.

However, it appears possible that in individual cases calls with suppressed number display in the business environment of competitors may be classified as a violation of the Unfair Competition Act (UWG).