Colonel Patrick Ryder, a spokesman for the US Central Command, said Junaid Hussain was specifically targeted in an air strike that killed him August 24 in Raqqa, Syria.
He declined to confirm reports that a drone was used to kill Hussain, but he said the British-born jihadist and propagandist was the sole casualty of the air strike.
Hussain was believed to be behind a number of cyber attacks, including on Central Command websites and Twitter accounts.
Ryder said he was responsible for "releasing personally identifying information of approximately 1,300 US military and government employees and specifically sought to direct violence against US service members and government employees."
"This individual was very dangerous," said Ryder. "He had significant technical skills."
Still, a US defense official said that as a hacker Hussain was not in the top ranks.
The information he posted about US military personnel was cobbled together from open sources on the Internet, and were not obtained by penetrating Pentagon computers, the official said.
In 2012, he was sentenced to six months in prison in Britain for illegally gaining access to former British prime minister Tony Blair's address book and publishing information from it.
He was also cited by two gunmen who attacked an exhibit featuring cartoon images of the Prophet Mohammed on May 3 in Garland, Texas.
In Twitter messages just before the attack, which was repelled by police, the assailants called on people to follow Hussain, who reportedly responded on Twitter after the shooting: "Allahu Akbar!!!! 2 of our brothers just opened fire."