(NEXSTAR) – The FBI issued an alert Tuesday warning of a massive spike in so-called “SIM swap” crimes over the last year.

Investigators are warning mobile carriers and the public of the scheme, which criminals use to empty people’s bank accounts, steal virtual currency and access personal information.

The FBI reported 320 such complaints between January 2018 and December 2020 – that number jumped to 1,611 in 2021.

During a SIM swap crooks often use phishing tactics or other methods to obtain enough of the victim’s personal information to impersonate them and trick the mobile carrier into switching the victim’s mobile number to another SIM card,

Sometimes, criminals will pay off employees of the mobile carrier to move a victim’s cell number to a SIM card in their possession.

In other cases, mobile company employees may fall for a phishing attempt that allows the criminal to hack into the system and swap the SIM data themselves.

Once a successful SIM swap happens, the criminals will have access to all of the victim’s calls, texts and other data, allowing them to reset passwords for bank accounts and other sites that use SMS-based two-factor authentication.

The FBI has the following recommendations for cellphone users:

  • Do not advertise information about financial assets, including ownership or investment of cryptocurrency, on social media websites and forums.
  • Do not provide your mobile number account information over the phone to representatives that request your account password or pin. Verify the call by dialing the customer service line of your mobile carrier.
  • Avoid posting personal information online, such as mobile phone number, address, or other personal identifying information.
  • Use a variation of unique passwords to access online accounts.
  • Be aware of any changes in SMS-based connectivity.
  • Use strong multi-factor authentication methods such as biometrics, physical security tokens, or standalone authentication applications to access online accounts.
  • Do not store passwords, usernames, or other information for easy login on mobile device applications.

If you think you may have been the victim of such a scam, contact the mobile carrier immediately to take back control of your number and reset online account passwords. Notifying financial institutions can help them detect suspicious log-in attempts.

The FBI encourages anyone who spots suspicious activity to notify their local FBI field office.