SIM swapping
Fraudsters get your mobile number transferred to their own SIM card and so receive your text-message codes. They use this to take over accounts that are only protected by SMS. Protection: 2FA via an app or security key instead of SMS.
AlsoSIM swapSIM swap fraudSIM hijackingnumber takeover
Criminals pretend to be you when contacting your mobile provider – claiming, for example, that your phone has been lost. They gather the details they need beforehand from the internet and social networks, or steal them through phishing. Once they have a SIM card with your number, calls and text messages go to them – including the confirmation codes from your bank or exchange.[1]
Why this affects Bitcoin owners
Whoever controls your number can take over an exchange account that can be reset by text message, or that protects logins and withdrawals only with SMS codes. In 2025, the FBI’s Internet Crime Complaint Center received 971 complaints about SIM swapping, with around $17.4 million in reported losses (all types of account, not just crypto).[2]
Warning signs
- Your phone suddenly can’t send texts, make calls or use mobile data – and poor reception isn’t the reason.[1]
- You get notifications about logins or password changes that you didn’t make.
How to protect yourself
- For exchanges and Bitcoin apps, use 2FAGlossaryTwo-factor authentication (2FA)Logging in with two independent proofs, such as a password plus a code from an authenticator app. For accounts with exchanges and Bitcoin apps, 2FA is a must – and SMS codes are the weakest option.On the learning path: Stage 4 · Step 3 – Buying Bitcoin →In the glossary → via an authenticator app or security key, not via SMS.
- Set up a PIN or security question with your mobile provider that you don’t use anywhere else.[1]
- Don’t make your mobile number the only way to recover an account.
- Share little personal information publicly.
- If it happens, contact your mobile provider, bank and exchange immediately.
Related terms
These terms are closely connected.
- This termSIM swapping
- Two-factor authentication (2FA)Logging in with two independent proofs, such as a password plus a code from an authenticator app. For accounts with exchanges and Bitcoin apps, 2FA is a must – and SMS codes are the weakest option.
- PhishingFraud using fake emails, text messages, websites or calls that look like genuine exchanges, wallet makers or banks. The goal is your passwords, 2FA codes – and above all your seed phrase.
- Custodian (custodial)A provider such as an exchange or app that holds the private keys for you. Convenient, because support can help if you lose your password – but you don’t hold the bitcoin yourself and depend on the provider paying out.
- Exchange (crypto exchange)A trading platform where buyers and sellers trade bitcoin with each other via an order book. The price results from supply and demand; fees usually follow the maker-taker model.
Explained in depth
These articles go into more detail:
- Stage 6 · Step 2Spotting scamsPhishing, fake support, investment and romance scams, AI fakes: how to spot 13 typical Bitcoin scams – and what to do if the worst happens.
- Deep dive · Stage 6Security checklistThree checklists to tick off – basics, your own hardware wallet, significant holdings: how to secure your account, wallet and seed phrase step by step.
More from „Wallets & security“
Sources2 sources · 2 publishers
The superscript numbers in the text refer to these sources.
- SIM-Swapping: Wenn Betrüger die Mobilfunknummer kapern (SIM swapping: when fraudsters hijack your mobile number) – Bundesverband deutscher Banken (Association of German Banks), 07.10.2021 (accessed 28/09/2026)
- Internet Crime Report 2025 – FBI Internet Crime Complaint Center (IC3), 2026 (accessed 28/09/2026)
This entry is for education only and is not investment, tax or legal advice.