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We often consider normal calls coming on mobile as just a medium of conversation, but a new investigation has raised concerns about the security of mobile networks and privacy of users. According to the report, in some circumstances the caller may get technical information to your phone even before the call is received.

This information may include the 15-digit IMEI number, smartphone model, and operating system version. That means the danger can start not just after picking up the call, but during the phone ringing itself.

After all, how can phone information be leaked through a call?

An investigation by Bayerischer Rundfunk (BR) revealed this potential problem. According to the report, this situation can arise especially when the person calling and receiving the call is using different mobile networks.

BR tested it through a total of 70 test calls on Germany's Telekom, Vodafone and Telefónica (O2) networks.

The investigation revealed that in some cases the IMEI number reached the called party through the Telekom and Telefónica (O2) networks. In some tests, information about the model and operating system version of the phone was revealed through Telekom and Vodafone networks.

However, Vodafone denied that the IMEI number was revealed in a test conducted on its network.

Why is IMEI number so important?

IMEI i.e. International Mobile Equipment Identity is a unique number, which is used to identify a mobile device.

It is different from the normal mobile number or SIM number. A device can be identified through its IMEI.

If any unknown person gets your phone's IMEI and other technical information of the device, then it can be used to create many types of risks.

According to the report, such information was used to:

To create a profile for a device,
run more targeted phishing campaigns,
For social engineering,
Identifying devices with outdated or vulnerable software

Can be done in works like.

IMEI of German MP's phone also confirmed

During BR's investigation, a test call was also made to the phone of former German military officer and Bundestag member Roderich Kiesewetter.

According to the report, the IMEI number revealed during the test was the actual IMEI number of his phone. This incident made the matter more serious, as it indicated that the leaked information was not just imaginary or false data.

Germany's Federal Office for the Protection of the Constitution also confirmed this problem and acknowledged that intelligence agencies could misuse such technical information.

More than 1,000 mobile operators alerted

After the matter came to light, the Global System for Mobile Communications Association (GSMA) warned more than 1,000 mobile network operators around the world.

Operators were advised to examine the technical arrangements of their networks and filter out non-essential data transmission that could impact users' privacy.

Network operators made improvements in Germany

After the report came out, Germany's mobile network operators talked about implementing necessary technical changes in the network and solving the problem.

However, an important point is that BR's investigation was limited to Germany's mobile networks. Therefore, this investigation cannot independently confirm whether the same problem exists in the networks of other countries or not.

Warning regarding IMEI in IETF documents also

Privacy risks associated with IMEI are not entirely new. Security and privacy aspects to IMEI are also discussed in the IETF's RFC 7254 and RFC 7255 documents.

According to these documents, IMEI can be used to identify and potentially track a mobile device. Therefore, transmitting it openly poses a risk of affecting the user's privacy.

Does the common user need to be afraid?

This check does not mean that during every phone call your IMEI definitely gets to the other person. The problem is reported to be to certain network conditions and technical settings.

Nevertheless, this case shows how important the data exchange taking place in the backend of mobile networks is to the security of user information.

The most important thing for users is to keep the phone and operating system updated regularly and avoid sharing the technical information of the phone with unknown people. At the same time, the biggest responsibility to prevent such problems lies with the mobile network operators and technical institutions.