T-Mobile has issued a press statement. Apparently they did the right thing.

Our investigation revealed that this third party was able to view the name and social security number of 400 customers. These customers were notified in writing of this incident. Customer credit card information was not accessed.

Safeguarding T-Mobile customer information is a top priority for the company. In late 2003, T-Mobile discovered that an unidentified person accessed a portion of one of its internal computer systems. We immediately took steps that prevented any further access to this system.

We immediately notified the United States Secret Service, and asked it to investigate this incident, and to find the hacker.

Our investigation revealed that this third party was able to view the name and social security number of 400 customers. These customers were notified in writing of this incident. Customer credit card information was not accessed.

In late 2004, with the assistance of T-Mobile, the Secret Service was able to apprehend Nicholas Jacobsen, the alleged hacker, who was recently indicted in California. We are pleased that he is being brought to justice.

This same person is also believed to be involved in other attempts to gain unauthorized access to customer information. The Secret Service is investigating these allegations, and T-Mobile is cooperating to the fullest extent, including with regard to the allegations that customer photos have been subject to unauthorized access.