SIM Swap Attacks Can Bypass Your Crypto Account Security

SIM Swap Attacks Can Bypass Your Crypto Account Security

Two-factor authentication does not always mean two layers of protection

When one of those factors is your phone number, it can be stolen without touching your device.

What a SIM swap attack actually is

A SIM swap happens when an attacker convinces your mobile carrier to transfer your phone number to a SIM card they control.

They do not need your device. They need enough personal information to impersonate you to customer support.

Once the transfer is done, all calls and SMS messages sent to your number go to the attacker's phone instead.

• Your SMS verification codes now go to them
• Password reset links delivered by text are intercepted
• Exchange accounts with SMS-based 2FA become fully accessible

This is not a theoretical attack. It has been used repeatedly to drain exchange accounts holding significant amounts of crypto.

Why crypto accounts are the primary target

Phone numbers are tied to exchange accounts, email accounts, and recovery flows at almost every major platform.

SMS-based two-factor authentication was designed to add friction. It does, but not enough when the number itself can be reassigned.

Attackers research targets in advance. Information shared publicly, such as exchange affiliations, wallet holdings, or crypto activity on social media, makes individuals easier to target.

Once inside an email account, an attacker can reset passwords across every linked service in minutes.

The hardware wallet primer explains why reducing reliance on any single point of failure is one of the most consistent principles in self-custody security.

How to reduce this risk

The goal is to remove your phone number from as many critical recovery paths as possible.

• Switch from SMS 2FA to an authenticator app such as Google Authenticator or Authy wherever exchanges allow it
• Use a unique, strong password for each exchange account and do not store them in a browser
• Remove your phone number as a recovery option for your email account if another method is available
• Request a SIM lock or port freeze with your mobile carrier to prevent unauthorised transfers
• Treat your phone number as semi-public, not as a security credential

Where hardware wallets fit in

SIM swap attacks target custodial accounts, exchanges, and services that hold crypto on your behalf. They cannot steal funds held in a self-custody hardware wallet.

When your private keys are stored on a hardware wallet and never exposed to any internet-connected service, there is no account to compromise and no recovery flow to exploit.

Wallets with a trusted on-device display go further by ensuring that transaction signing happens only on the physical device, isolated from any software running on your computer or phone.

Moving holdings off exchanges and into self-custody removes the entire attack surface that SIM swap attacks depend on.

A real world scenario

A user kept the majority of their crypto on an exchange account protected with SMS-based two-factor authentication.

An attacker gathered enough personal details from public social media profiles to impersonate the user to their mobile carrier.

The phone number was transferred within a single support call.

Within an hour, the attacker had reset the account email, bypassed 2FA, and withdrawn all available funds.

The user's device was never accessed and no malware was involved.

Unsure how to reduce your exposure to account-level attacks

Some users prefer keeping funds on exchanges for convenience.

Others have already moved holdings to self-custody but still use SMS 2FA for linked email accounts.

The right setup depends on how much of your security currently relies on your phone number.

You can use our wallet selector to find a suitable hardware wallet based on your holdings and how you store crypto today.

Find the right wallet in under a minute

Final thought

An exchange account is only as secure as its weakest recovery path. Self-custody removes the recovery path entirely.

Crypto Compass is published by Bitcoin Wallet SG, a Singapore authorized hardware wallet reseller.