"In an advisory posted on an FBI Web site, officials warned Internet service providers worldwide to be on the lookout for "self-described 'patriot' hackers [targeting] those perceived to be responsible for the terrorist attacks" of the Pentagon and World Trade Center."
Eric Lichtblau, James Gerstenzang, "After the Attack," Los Angeles Times, September 18, 2001
Although today's term has been much in evidence lately in light of the recent atrocities in New York and Washington, the phrase has been around for a few years. The earliest citation I could find is the following AP headline:

"Soldier Charged with Computer Espionage Was Patriotic Hacker, Family Says"
The Associated Press, August 21, 1996
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In this case, however, the "hacker" was a soldier who gave computer passwords to a Chinese citizen. His lawyer and family claimed that he was only trying to show his superiors there were problems with an "expensive, supposedly impenetrable system."