How can I tell if someone is trying to hack port 8333? I am experimenting with leaving a public replica of the Bitcoin chain on the internet.  In doing so I'm actively monitoring the debug output so I can get a sense of what is happening with the inbound connections.

How can I tell what the clients are doing and respond appropriately? 

Under what criteria should I block a port to an IP address, subnet, etc?
You are looking for ways to improve the client's protections against flaws? 

Here's a list of its current protections:


http://en.bitcoin.it/wiki/Weaknesses#Denial_of_Service_.28DoS.29_attacks