T-Mobile Says Hacker Used Specialized Tools, Brute Force (1)

T-Mobile US Inc. said a cyberattack earlier this month that exposed millions of customer records was carried out using specialized tools to gain entry to the network, followed by brute force-style hacking techniques to access user data.

“In short, this individual’s intent was to break in and steal data, and they succeeded,” Chief Executive Officer Mike Sievert said Friday in a statement, the company’s fullest account yet of what happened. The company has hired cybersecurity provider Mandiant Corp. and consulting firm KPMG LLC to improve its defenses, he said.

The breach, the fourth that has compromised T-Mobile customer records ...