You'll never find a lawyer who would go after this from a terrorism angle. You will, however, find many lawyers looking for an easy civil case.
Since the offender appears to be English (or have I got that wrong?), how would AVSIM press their case? Hire a British lawyer and pursue it entirely within their system, under English law? Or since the crime and damage was done to an American firm, and to a server located on American soil (I'm presuming), does U.S. law apply? If so, would/could the accused be extradited to stand trial in the U.S.? Was the crime committed in England or America?
Clearly, I am completely ignorant of international law, especially as it applies to the borderless "interwebs."