A SIM swap attack is when a scammer takes over your phone number by convincing your mobile carrier to move it to a SIM card they control. From that moment, your calls and text messages go to them. That includes every SMS login code and password reset link. In crypto, that is often all it takes to empty an exchange account. Someone tried it on me once, and I’ll share how that went below.
SIM swaps are back on everyone’s mind this week. On Tuesday, contact data for Coinbase customers leaked through an analytics vendor, and phone numbers are exactly what SIM swappers hunt for. Here is how the attack works, how to spot it, and how to make sure it never works on you.
How a SIM Swap Attack Works
A SIM card ties your phone number to your device. Carriers can move a number to a new SIM, which is normal when you lose a phone or upgrade. SIM swappers abuse that exact process.
A typical attack runs in four steps:
1. Gather data. First, the attacker collects your name, phone number, email and sometimes your address or date of birth. Data leaks, social media and phishing all supply this.
2. Fool the carrier. Next, they contact your carrier pretending to be you. They claim a lost phone or a broken SIM and ask for the number on a new card. Some gangs skip the acting and bribe a store employee instead.
3. Take the number. Once the carrier agrees, your phone loses service. Meanwhile, the attacker’s phone now receives your calls and texts.
4. Reset everything. Finally, they hit “forgot password” on your email and exchange accounts. The reset codes arrive by SMS, straight to them. Within minutes, they log in, change your settings and withdraw your crypto.
The scary part is the speed. Victims often notice only when their phone shows “No Service,” and by then the withdrawals may already be on-chain.
Someone Tried to SIM Swap Me
This isn’t theory for me. In 2018, when I had a T-Mobile subscription, someone tried it on my number.
The attacker opened a support chat with T-Mobile, pretending to be me, and asked for a new SIM card. They knew my full name, my home address and my date of birth. They even knew my girlfriend’s name at the time. In other words, they had everything a support agent usually checks.
Luckily, T-Mobile emailed me the chat history. Reading it, I knew exactly what was happening. So I rushed to the nearest T-Mobile store and told them someone was trying to take over my number. To their credit, T-Mobile acted fast and shut the attempt down. I also filed a police report and got the numbers of the police officers in my area. In case something happened.
That scare changed how I set up my accounts. Afterward, I bought a prepaid SIM card and put it in a burner phone. Nobody has that number, and I only use it for a few account recoveries. After all, a scammer can’t hijack a number they don’t know exists.
In crypto, this is a serious threat. Your phone number can be the weakest link in your whole setup, no matter how good your wallet is.
Why Crypto Holders Are the Favorite Target
Banks can reverse a fraudulent wire. Crypto transactions, on the other hand, are final. Once coins leave your account, nobody can pull them back, which makes crypto the perfect payday for a SIM swapper.
The numbers back this up. In 2022, the FBI logged 2,026 SIM swap complaints with $72.7 million in reported losses. By 2024, that dropped to 982 complaints and about $26 million. Part of that fall came after the FCC forced US carriers to tighten SIM change rules in late 2023. Still, those figures undercount the real damage. Many SIM swaps get reported as account takeovers or crypto theft instead.
Some cases made headlines:
- FTX: hours after the exchange filed for bankruptcy in November 2022, hackers drained over $400 million. The DOJ later charged three people with using a SIM swap to pull it off.
- Michael Terpin: the early crypto investor lost about $24 million after a SIM swap on his AT&T number. A court later awarded him over $75 million against the attacker.
- Vitalik Buterin: in September 2023, attackers hijacked his T-Mobile number and used his X account to post a wallet drainer link.
- Poland, June 2026: police arrested four members of a gang that breached telecom partners to run SIM swaps. With help from the FBI, they tied the group to millions stolen from exchange accounts.
Data Leaks Make SIM Swaps Easier
A SIM swap starts with information. The more an attacker knows about you, the more convincing they sound to your carrier.
That is why every leak matters, even ones without passwords. This week, customer emails and phone numbers leaked in the Coinbase data breach through vendor Amplitude. In August, a shipping partner exposed names and addresses in the Trezor data breach. Each leak hands scammers two things: your contact details, and proof that you own crypto.
Even claimant portals aren’t safe. Back in 2023, a SIM swap on one Kroll employee exposed data for FTX, BlockFi and Genesis creditors. As a result, people who had already lost money got targeted a second time.
Warning Signs of a SIM Swap
Most victims get one or two clues before the money is gone. Act immediately if you notice any of these:
- Your phone suddenly shows “No Service” or “SOS only” in an area with normal coverage
- You get a text from your carrier about a SIM change or number transfer you didn’t request
- Calls and texts stop arriving, while friends say your phone rings
- Password reset or new login emails show up from your exchanges or email provider
- You can’t log into your email, even with the right password
A single dead signal can be a network issue. However, a dead signal plus unexpected security emails is a SIM swap until proven otherwise.
What to Do If You Get SIM Swapped
Speed matters more than anything here. Every minute counts, so work through this list in order:
1. Call your carrier from another phone. Report the fraudulent SIM change and ask them to restore your number. Request a fraud flag on the account too.
2. Lock your exchange accounts. Most major exchanges let you freeze an account from their website or through support. Do this before you do anything else online.
3. Secure your email. Change the password from a clean device and sign out all other sessions. Your email is the master key to everything else.
4. Remove the phone number. Once you’re back in, drop SMS as a login and recovery method everywhere.
5. Report it. In the US, file a complaint with the FBI’s IC3. Elsewhere, contact your national cybercrime unit. Reports help when funds get traced later.
If crypto already left your account, read our guide on whether stolen crypto can be recovered. Recovery is rare, but quick action improves the odds.
How to Protect Your Crypto From SIM Swaps
The good news is that a SIM swap only works if your phone number unlocks something. Take that power away and the attack becomes useless.
Stop using SMS for two-factor. Switch every exchange and email account to an authenticator app, a passkey or a hardware security key. Of these, a hardware key offers the strongest protection.
Remove your phone number from account recovery. Many services let you reset a password by SMS. Turn that off wherever you can. Where a number is required, use a private one, like a prepaid SIM that nobody knows about.
Add a carrier PIN or number lock. Most carriers offer a port-out PIN, SIM lock or number lock. With it, nobody can move your number without a code only you know.
Protect your email first. Give your crypto email a unique password and hardware-key 2FA. Better still, use a separate email address that you never post publicly.
Turn on withdrawal allowlists. With an allowlist, an exchange only sends funds to addresses you approved in advance. Even if someone gets in, they can’t withdraw to their own wallet.
Keep long-term holdings off exchanges. A SIM swap can’t touch coins in your own wallet. A cold wallet keeps your keys offline, and our self custody vs exchange guide explains when each option makes sense.
Never store your seed phrase digitally. No photos, no notes app, no cloud backups. Our seed phrase vs private key guide explains why that phrase is the real key to your funds.
Share less. Keep your phone number off social media, airdrop forms and public profiles. Every place it appears is one more place it can leak from.
SIM Swaps vs Phishing and Wallet Drainers
SIM swaps target your accounts. Phishing and wallet drainers, by contrast, target your wallet directly. Many attacks combine them. For example, a scammer might use your leaked number to text you a fake “security alert” link.
So the defenses overlap. Always verify links, never sign transactions you don’t understand, and learn how to avoid wallet drainer scams. For a full checklist across every type of attack, see our stay safe page. You can also find every hack and breach we’ve covered in our security guides.
Keep This Content Free
Security guides like this one stay free, because the people who need them most are usually new. If it helped, support the site by opening an exchange account through our links. Just remember to set up app-based 2FA on day one.
Final Words
A SIM swap attack turns your phone number into a master key for your accounts. Attackers fool or bribe your carrier, take your number, and reset your passwords by SMS. Losses run from a few thousand dollars to hundreds of millions.
Fortunately, the fix is simple. Drop SMS two-factor, lock your number with your carrier, secure your email, and keep long-term holdings in your own wallet. Do it today, before your number shows up in the next data leak. New to crypto security? Our knowledge base collects all the beginner guides in one place.
FAQ
What is a SIM swap attack?
A SIM swap attack is when a scammer gets your mobile carrier to move your phone number to a SIM card they control. They then receive your texts and calls, including SMS login codes and password resets.
How do hackers do a SIM swap?
They gather personal data about you from leaks or social media. Then they impersonate you to your carrier, or bribe a carrier employee, to transfer your number to their SIM.
How do I know if I’ve been SIM swapped?
Common signs are sudden “No Service” on your phone, a carrier text about a SIM change you didn’t make, and unexpected password reset emails. If you see these together, act immediately.
Can a SIM swap steal crypto from a hardware wallet?
No. A SIM swap gives access to accounts that rely on your phone number, like exchanges and email. Crypto in your own hardware wallet stays safe, as long as your seed phrase is never stored online.
What is the best protection against SIM swaps?
Stop using SMS for two-factor authentication. Use an authenticator app, passkey or hardware security key instead, and add a port-out PIN or number lock with your carrier.
Can I get my crypto back after a SIM swap?
Rarely. Crypto transactions are final, so recovery depends on tracing funds and fast reports to your exchange and law enforcement. Prevention is far more reliable than recovery.
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