The hacker group known as LulzSec appears to be back after many months of lying low, saying it has obtained email addresses and other information about nearly 171,000 users of MilitarySingles.com, a commercial dating site.
The group, which in 2011 went after government agencies and companies including the FBI, CIA, Sony and even PBS, said many of the email addresses include @us.army.mil and other addresses reserved for the military.
The website bills itself as "the dating site for single soldiers and those interested in meeting them."
The Pentagon could not be reached for comment.
The programmers of the website are investigating the claimed attack and are taking measures to increase security, said Robert Goebel, chief executive of ESingles Inc., which owns the site.
"Regardless of whether it was a true claim or false claim," he said, "we're treating it as though it's true just to be safe."