I'm considering titles for my book, and every time I think of a title, I do an internet search to see if the title has already been taken. One of the titles "Hack, Hack. Who's there?" is not taken by any book known to Google; however, this is the title of a talk given at a conference on internet security earlier this year. So, the main question: would there be any legal problem in using this title? A secondary question: would the title, even if being legal, be advisable because it could get mixed up with this talk?
Is there a connection to the internet security conference? Like, could they reasonably think you were trying to build off their success? Is your book fiction? It's pretty difficult to come up with a completely original title, especially with the hundreds of thousands of new books coming on the market every year. So I wouldn't worry about an accidental overlap. But it might be a bit confusing if you wrote a non-fiction book on the same topic as the talk, with the same title.
It's only a problem if there is a legitimate case for confusion between your work and another. You can't call something The Catcher in the Rye because people will expect the Salinger book. But you can call something Fireblade, despite there probably being a dozen unknown works out there sharing the title.
AFAIK, titles of books, songs, or stories cannot be copyrighted. But they can be trademarked, so you can't use "Star Trek" or "Star Wars" in your title unless you're doing it under license. However, if your title is not a protected trademark, but is a quote from the content of another work, you must receive permission from the copyright holder of the work. I am not a copyright lawyer, just a guy who recently researched the subject.
There's no legal problem as far as I can tell. Besides, how many people would know about the conference in the first place? I've been to several conferences, and I don't even remember any of the titles of the talks given.