How can I stop Linux from sending ICMP "Destination Unreachable" responses?

Dave asked:

I have a Linux system which has a number of services disabled (for example, telnet). When a telnet client attempts a connection, the system responds with an ICMP “Destination Unreachable”. Is there a way, short of modifying the Linux network stack, to disable this behavior?

My answer:

The destination unreachable ICMP packet is a standard Internet control message which indicates that there is no service available on that port. There’s generally no reason to disable it (and you didn’t give one).

But if you really want to disable it, you can just change your firewall rules to drop packets rather than rejecting them. (Wait, you are firewalled, right?)

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