The dangers of youth, eh ?
Going back, the way this was dealt with physically, by some banks, was to introduce a physical barrier - a lobby - between the outside world and the internal systems. Entrance to the lobby did not require access to back office systems but did keep out a high number of otherwise wannabe miscreants.
So how can that be rolled into a virtual landscape ?
(That's a rhetorical question, by the way. The solution is out there waiting for someone to ask the question.)