A hacker who passed a list of American military personnel to the so-called Islamic State group could face up to 25 years in jail.
Kosovan Ardit Ferizi pleaded guilty to charges of providing material support to America’s enemies, in a court hearing in Virginia.
The maximum sentence for that crime is 20 years in jail.
He could also be sentenced to a further five years in jail for hacking into a federal computer to steal the list.
“Ferizi endangered the lives of over 1,000 Americans,” said US attorney Dana Boente in a statement from the Department of Justice.
The DoJ said: “The case against Ferizi is the first of its kind, representing the nexus of the terror and cyber-threats.”
It said Ferizi, who is now 21, handed the list to IS, knowing it could incite the group to attack the individuals named in it.
Information about the names, email addresses, passwords, locations and phone numbers for about 1,351 military personnel and federal staff came from several servers that Ferizi hacked into.
He targeted both machines in US government offices and corporate computers.
During the court proceedings, Ferizi admitted he had passed the list to Junaid Hussain, a British cyber-expert involved with IS who was killed in August last year by an air strike.
“I don’t know myself why I did this. I still ask myself why I committed this crime,” the Washington Post reported that he had said in court.
Ferizi, who used the Twitter name @Th3Dir3ctorY, was arrested in Malaysia in October 2015 and extradited to the US in January this year.
He is due to be sentenced on 16 September.
After he has served his sentence, he will be deported to Kosovo and barred from re-entering the US.