Not one entity, not even the Patriot Act or the Computer Fraud and Abuse Act has an absolute definition for "hacking".
You asked a question about ethics, not law, so don't starting dragging pseudo-legalese into this. Particularly when you, yourself posted,
Legality aside, what would you do?
Although the two often overlap, ethics and law are not the same thing. And it also should be kept in mind at all times in an ethics discussion that the word
ethics comes from the Greek
ethos, meaning "character".
First, when you are given permission to use some else's property, there are always explicitly- or implicitly-defined limits to what you can do with the property, and you have an ethical obligation to abide by those limits.
If I loan you my car to go to the supermarket, you would be behaving unethically to drag-race in my car. You have violated the implicit limits on the use of the car.
So your most ethically-correct behavior would have been:
E. to not have been screwing around on someone else's network in the first place.
Because when the organizers of the meeting granted you permission to use the network, I do not think it reasonable to expect that they intended that you would use the network to scan other participants' computers.
Second, it is unethical to use someone's property without his permission.
The fact that you might do less harm than a hostile hacker does not give you permission to use the property -- that's saying you somehow have permission to use my car any time you like simply because less-responsible someone else who might have used it would have wrapped the car around a tree.
The fact that you have the best of intentions does not give you permission to use the property. That's saying you have permission to use my car any time you wish so long as you get the car a tune-up and leave it back with me with a full tank of gas.
So option A is unethical. And I don't think anyone would argue that B and C are unethical, too.
But what
should one do? I would, understanding that the organizers would be reasonably expected to be disapproving of my scanning their network without permission, contact the organizers of the event and tell them what I found out and how. And I would accept with good grace whatever reasonable penalty they imposed. (And as an aside, getting banned from that network for the rest of the event is a reasonable penalty for scanning their network -- after all, it's their network and they can withdraw whatever use-permissions they have granted.)
Want the best answers?
Ask the best questions! TANSTAAFL!