One of the world's foremost IT security experts has been denied entry to the United States, where he was a featured speaker at the annual Black Hat security conference.
Thomas Dullien, known as 'Halvar Flake' in hacker circles, has spoken at the Black Hat conference for the past seven years.
The well-regarded reverse engineering genius says he was blocked from entering America after customs found 'training materials' in his luggage.
In his blog, Dullien says he was held for over four hours after his nine hour flight from Germany.
"The largest part of the attendees of the trainings (sic) are US-Government related folks, mostly working on US National Security in some form," he writes.
"I have trained people from the DoD, DoE, DHS and most other agencies that come to mind.
"Each time I came to the US, I told immigration that I was coming to the US to present at a conference and hold a training class. I was never stopped before."
Dullien says electing to use the US visa waiver programme contributed to him being turned around by US Customs and sent back to Germany.
Reaction on his ADD/XOR/ROL blog has been quick to condemn the immigration debacle.
"As a US citizen and an attendee of Black Hat USA 2007, I am embarrassed and ashamed by the treatment that you've been subjected to. Hopefully we can get some media coverage of your situation and push the US Gov't to reconsider its decision," wrote one disappointed reader.