Telegram’s Anonymity Hole: How to get any user’s phone number

Earlier on we talked about how Telegram is a product of marketing campaigns, with no real proof of security attached — simply because security sells well.

Today we present a simple opportunity to obtain the phone number of any user within any Telegram-group, linked to the systematic work of the official application.

Have you ever thought why Telegram needs your phone number to begin messaging? It’s an obsolete and insecure mechanism, allowing access to all of your messages via social engineering or intercepting one SMS. But the worst problem with using a phone number is that it’s used for your identification, binding all messages to your identity. Thinking about Telegram as a secure-messenger, people will allow themselves to write private information.

If you believe that your phone number is only available to Telegram: You are wrong, it is available to anyone.

How to access any Telegram user’s phone number

The screenshot below demonstrates our initial chat (open group). Let’s direct our attention to the user “Sergey Lebedev”.

Now we leave the application, and go to the normal contacts of the device. There we register a new contact with any name (“Testing Phone ID”) and enter any phone number.

After adding and saving the contact in the device’s contact book, we return to Telegram.

In the privacy settings (Settings — Privacy and Security) let’s make sure that the synchronization of contacts is enabled. This function adds all device contacts to the application if they are already registered in Telegram.

After completing the above actions, one more user will be added to the contacts of the application, if the person with this phone number has already been registered in the Telegram.

In our case, we guessed and everything went smoothly. The first telephone number existed in the Telegram system.

As we can see, the user’s photo looks like it was in the beginning. Such an image is possessed by “Sergey Lebedev”. But now, due to the addition of a phone number to the contact list of the device and their synchronization with Telegram, “Sergey Lebedev” has become user “Testing Phone ID”, as it will be displayed in the future. Telegram changed the username to what we wrote into our contact-list.

Now, we go to the first chat and see that the name has changed to what is written in the phone contacts.

Thus, we could obtain any user’s phone number.

You can say that’s not so simple. There are many phone numbers, which make that approach ineffective. But in the real world, there are some tricks:

  • Social engineering helps to reduce range of phone numbers by thousands. You can ask user by country (you’ll get the country code), carrier name they use (some more leading digits).
  • If you have 10, 20, or even 100 numbers, including exactly what you need, the situation no longer seems so complicated.
  • Simple application can be written for mobile phones, which adds any range of phone numbers to mobile’s address book.

This is a critically dangerous possibility, which can be used in a variety of ways. Of course, this is a huge hole in the system of storage, security and protection of personal data for Telegram users. It poses a threat to the security layer of any user registered within the messenger, especially investors, businessmen, politics, celebrities, public people, etc.

Also, Telegram allows you to find the real names of users with a phone number.

Remember, if an application asks you for credentials as a phone number, there may be hidden intentions. This relates not only to Telegram, but also to Signal, WhatsApp, Viber, and other social-messaging applications.

We are sure the future of messaging in terms of anonymous blockchain technology: ADAMANT Messenger.

Take care of your data.