Three journalists working for a French security magazine were expelled from the Black Hat security conference after allegedly hacking into the press-room computer network.
The journalists work for Global Security Mag, a media sponsor of the conference in Las Vegas.
Black Hat said the three were ordered to leave the conference and barred from Defcon, a sister security conference.
One of the journalists, Marc Brami, director of the magazine, told CNET News the incident was "a joke" but he was not responsible for it.
"It is not good for my magazine, but also it is not so good for Black Hat," he said. "Maybe they lost a good supporter. For us, it was like a joke."
The journalists were seen huddled over a table in the two press rooms and were said to have obtained usernames and passwords of journalists at the conference.
CNET News was one of the alleged victims, although it said the username and password displayed in a list were inaccurate. But a journalist from another magazine confirmed that the username and password he used had been exposed in the list.