Ken Jones writes:
> My understanding is letting in udp packets on ports >1023 is generally
> safe, as the only listeners on those ports are clients such as archie
> waiting for a specific response.
This does not agree with my experience. This assumes that the intruder
will not find a bug in another service permitting them to start a server
inside your network to listen on a port >1023.
For example, they might exploit an un-repaired (or unknown) sendmail
problem to deposit an FSP server on your system to which they can then
connect and pick up password files, proprietary documents, etc.