According to the telecoms giant, the breach took place “several weeks ago” and the attackers used stolen login credentials to gain access to internal systems.
T-Mobile said the attackers did not steal customer or government information during the attack. The company was able to cut off the attacker’s access to its network and disable the credentials after discovering the breach.
According to Brian Krebs, who first reported the breach, the cybercriminals stole proprietary T-Mobile source code during the attack.
The breach means T-Mobile has suffered seven privacy breaches since 2018.
In December 2020, hackers gained access to customer network information such as phone numbers and call records. In 2021, an internal T-Mobile application was accessed by attackers without authorization.