Signaling System 7 (SS7) flaws could allow hackers to listen in private phone calls and read text messages on a potentially vast scale, despite the most advanced encryption used by cellular networks. Global cellular networks have consistently been ignoring this serious issue, saying exploitation of the SS7 weaknesses requires significant technical and financial investment, so is a very low risk for people. White hat hackers demonstrated how cybercriminals could exploit SS7 flaw to take control of online bitcoin wallets to steal all your funds.
Source: https://thehackernews.com/2017/09/hacking-bitcoin-wallets.html