A teenage hacker who said he broke into computer systems across the country and helped others attack the White House Web site pleaded guilty yesterday in federal court to one count of computer intrusion.

Eric Burns, 19, of Shoreline, Wash., who used the cyber nickname "Zyklon," was indicted in May by a federal grand jury. He was accused of breaking into three Washington area computer systems, including the one used by the U.S. Information Agency.

Prosecutors agreed to drop two of the three charges in exchange for Burns's plea and for his agreement to pay $36,240 in restitution. He is scheduled to be sentenced in November and faces a fine of up to $250,000 and a maximum prison sentence of five years.

Burns told authorities that he also had managed to alter World Wide Web sites used by Vice President Gore and NATO, among others.

Helen F. Fahey, U.S. attorney for the Eastern District of Virginia, said yesterday that she expects Burns will spend some time in prison.

"Burns's hacking caused many people to have to spend many, many hours correcting the problems he caused," Fahey said.

Some hackers have argued that they do a valuable service by pointing out the security flaws in supposedly secure computer systems, but Fahey said that "Burns's hacking was no more of a service than the actions of a burglar who defeats a weak alarm system and cleans out the entire contents of his victim's house."

According to court records, Burns admitted to attacking six computer systems, which he infiltrated by using the Internet. Using a program he designed and called "Web Bandit," Burns scanned sites on the Web, searching for vulnerable computer systems. He would infiltrate systems and arrange for visitors to see a Web page of his own design.

Burns hacked four times into the computer server at Electric Press in Reston, which was the host of Web pages for the USIA, NATO and Gore. All those sites were altered. The attacks, investigators said, also affected U.S. embassy and consulate Web sites and others that depended on the USIA for information.

One attack made thousands of pages of information unavailable and resulted in officials closing down the USIA Web site for eight days.

Burns made his final assault onto the Electric Press server on Jan. 22 when investigators say he replaced the USIA page with one that read: "United States lack of information agency . . . surely, after you get hacked twice . . . and reinstall . . . you can learn from it . . . oh yeah, you're clueless."

Burns also was known for leaving love notes for a high school classmate named Crystal on the Web pages he defaced, and he was fast making a name for himself in the underground world of computer hacking when he got caught this year.

In May, the White House Web server was attacked, and an attempt was made to replace it with a page that contained references to Zyklon and Crystal. The White House was alerted, shut down its server and disconnected its public and private computer networks from the Internet for two days.

Burns took credit for the attack during an Internet chat session, but according to court records, he told the court that he was not responsible for the attack and instead had provided advice to others about how to do it.