The practice of “SIM swapping”” refers to crooks working with telco employees to port a user’s phone number to a SIM card under an attacker’s control for a short period. The attacker uses access to the victim’s number to log into their online accounts protected with SMS-based one-time tokens. Attacks using SIM swap tactics have been used to steal cryptocurrency funds but also to take over high-value social media accounts with valuable usernames
Source: security