The prosecutor with whom I was speaking, by the way, was Mark Eckenwiler. He's Senior Counsel in the Computer Crime and Intellectual Property Section, Criminal Division, U.S. Department of Justice. His areas of responsibility include federal wiretap law, computer search and seizure, and online investigations.
I got the same response from Richard P. Salgado, who is a trial attorney in the Computer Crime and Intellectual Property Section of the Criminal Division of the United States Department of Justice. Mr. Salgado specializes in investigating and prosecuting computer network cases, such as computer hacking, denial of service attacks, illegal sniffing, logic bombs, viruses and other technology-driven privacy crimes.
Others who asked similar questions on the topic received the same answer: It's illegal.
Keep in mind it's these people's jobs to say that. However, you'd need a very good, tech-savvy and cyberlaw-savvy defense attorney to counter their arguments.