how-to block ads
• If a UDP port is probed and a PORT UNREACHABLE packet comes back, the port is marked as closed.
• If a UDP port is probed and nothing comes back, it is marked as open.
If you block only certain UDP ports, then strangely, you appear to have those ports open to a scanner. It is better to simply block response from ANY and ALL UDP ports. That way, you are not giving away any information at all.