LOS ANGELES — A hacker who broke into the network of Bellevue-based T-Mobile USA and accessed personal information on hundreds of customers, including a Secret Service agent, has pleaded guilty to a felony hacking charge.

Nicholas Lee Jacobsen, a 21-year-old computer engineer who now lives in Oregon, entered his plea Tuesday in U.S. District Court in Los Angeles. He faces up to five years in federal prison and a $250,000 fine when he is sentenced May 16.

The break-in targeted the network of T-Mobile USA, which has 16.3 million customers nationwide. It was discovered during a broader Secret Service investigation.

T-Mobile acknowledged the hacker was able to view the names and Social Security numbers of 400 customers, all of whom it said were notified in writing about the break-in, which lasted at least seven months.

The company said customer credit-card numbers and other financial information were not revealed.

Prosecutors alleged Jacobsen posted a notice on an online bulletin board that said he could look up the name, Social Security number, birth date and passwords for voice mails and e-mails for T-Mobile customers.

Jacobsen was accused of targeting the desktop computer of a Secret Service agent on his trail. The agent, Peter Cavicchia, also was a T-Mobile customer and sometimes used the wireless network to communicate about the case, unaware it wasn't safe.

Jacobsen was arrested in October in Orange County, where he used to live, and he later was released on $25,000 bail.