Destination unreachable administratively prohibited messages can inform the hacker to what?

Circuit-level proxies operate at the session layer and silently relay or drop connections rather than generating ICMP administratively prohibited messages back to the sender.

Honeypots are designed to emulate legitimate services and attract attackers - they would not advertise their presence by sending administratively prohibited ICMP responses.

Malformed packets would typically cause application-layer parsing errors or silent drops, not a standardized ICMP Type 3 Code 13 response from a router.

ICMP Type 3 Code 13 is generated by routers and firewalls when an access control list or firewall rule explicitly denies a packet rather than the destination being simply unreachable. Receiving this message tells an attacker that an active filtering device is present and enforcing policy, which discloses the existence and approximate rule set of that security control, making it useful reconnaissance information.

An administratively prohibited message is an explicit security denial, not an indicator that the network is functioning without restrictions.