A Massachusetts teenager has pleaded guilty to hacking into the cell phone account of hotel heiress and Hollywood celebrity Paris Hilton.

The 17-year-old was sentenced to 11 months' detention at a juvenile facility for a string of crimes that include the online posting of revealing photos and celebrity contact numbers from Hilton's phone. As an adult, he will undergo two years of supervised release in which he will be barred from possessing or using any computer, cell phone or other electronic equipment capable of accessing the Internet.

The U.S. Attorney's Office for Massachusetts and the state district court declined to identify the teenager, noting that federal juvenile proceedings and the identity of juvenile defendants are under seal. But a law enforcement official close to the case confirmed that the crimes admitted to by the teenager included the hacking of Hilton's account.

The teenager also pleaded guilty to making bomb threats at two high schools and to breaking into a telephone company's computer system to set up free cell phone accounts for friends. He also participated in a group attack on data-collection firm LexisNexis Group that exposed personal records of more than 300,000 consumers. Prosecutors said victims of the teen's actions have suffered about $1 million in damage.

Investigators began focusing on the teenager in March 2004 when he sent an expletive-laced e-mail to a Florida high school, threatening to blow it up, according to a statement from prosecutors. The school was closed for two days while a bomb squad, a canine team, the fire department and other emergency officials examined the building.

The teenager told washingtonpost.com in an interview for a story this year that he also broke into the network of Dulles-based America Online Inc. AOL did not return calls seeking comment. Washingtonpost.com is not revealing the teenager's name because he communicated with a reporter on the condition that he not be identified. It is Washington Post policy to not name juvenile offenders.

In January, the teenager hacked into the telephone-records system of T-Mobile. He used a security flaw in the company's Web site that allowed him to reset the password of anyone using a Sidekick, a pricey phone-organizer-camera device that stores videos, photos and other data on T-Mobile's central computer servers. A month later, the teenager used that flaw to gain access to Hilton's Sidekick files, according to corroborating information and screen shots he shared with washingtonpost.com.

The Justice Department said the investigation of the teen's associates is continuing, but it remains unclear how many of those individuals will be prosecuted. In May, Secret Service and FBI officials served search warrants on at least nine people thought to be connected to the hacking ring of which the teen was a member, known as the Defonic Team Screen Name Club or DFNCTSC for short.

Krebs is a staff writer for washingtonpost.com.

Photos and contact numbers from Paris Hilton's phone were posted on the Web.