Masternodes do provide a nice easily identified target - I think some effort on testnet is needed at some point soon, maybe after RC4 release, to try and break testnet MNs with such attacks and figure out what we can implement to mitigate them, because we can't stop them.
I don't know a lot about it, maybe we have a white hat among us who can assist?
You're thinking what I'm thinking, I was looking around last night to hire someone as an exercise to penetration test my masternodes...