Telegram and WhatsApp are both known for their security and end-to-end encryption and latest forward way secrecy techniques which secure end user data in a good manner. All these security features still doesn’t stop hackers from Hacking into WhatsApp or Telegram using a very known and old exploit of Signaling System 7 (SS7) .
SS7 Hack Demo -Hacking WhatsApp / Telegram
How the Hack is executed ?
Above demonstrated hack DOES NOT break WhatsApp and Telegram Encryption rather it exploits the weakness of SS7. This is done by tricking the cellular network into believing that the Attacker’s phone has the same number as the target’s. From there, the attacker would create a new WhatsApp or Telegram account and receive the secret code that authenticates their phone as the legitimate account holder. Keep in mind this technique would literally work on any Network and any Online Messaging Service , once you spoof the number you can pretty much do everything.