As the world becomes increasingly digital, it’s important to be aware of how to ensure that you’re safe. A recent case from the Department of Justice may help as a cautionary tale after hackers were found to have stolen $2.4 million in cryptocurrency.

The hackers in question are six people across the United States and in Ireland connected to a group known as “The Community.” They caught charges for conspiracy to commit wire fraud, wire fraud and aggravated identity theft.

According to the Department of Justice, the hackers took part in something called “SIM Hijacking” or “an identity theft technique that exploits a common cyber-security weakness – mobile phone numbers.”

Essentially, the hackers convince, bribe, or otherwise trick mobile phone carriers into transferring a phone number to a new SIM card. With a phone number, hackers can then reset passwords and by-pass security measures like two-factor authentication.

“Mobile phones today are not only a means of communication but also a means of identification,” United States Attorney Matthew Schneider said.

It’s estimated that the hackers used this technique seven times to target people’s cryptocurrency wallets. Three of the people currently charged are employees of mobile phone service providers, who helped The Community steal people’s identities in exchange for bribes.

“This case should serve as a reminder to all of us to protect our personal and financial information from those who seek to steal it,” Schneider said.