German security expert denied entry to the US for carrying training materials on analyzing software for security vulnerabilitiesThomas Dullien, who's also known by the nickname Halvar Flake, was denied entry into the U.S. because he was contracted to speak at Black Hat as a private individual and not as a representative of his company, according to a post on his blog. He was refused entry after customs officials found training materials he had packed in his luggage, it said. Dullien, the CEO and head of research at Sabre Labs, was scheduled to conduct a two-day training course at Black Hat on analyzing software for security vulnerabilities. The session, set to start on Monday and limited to 18 attendees, was sold out.