Firewalk has just completed the second phase (the scanning phase) and a technician receives the output shown below. What conclusions can be drawn based on these scan results? TCP port 21 - no response

This is incorrect because the TTL exceeded response on port 23 proves the firewall is NOT blocking port 23 - the packet passed through. Additionally, Firewalk cannot determine whether a service is listening on the target host from this result alone.

No response in Firewalk indicates firewall filtering, not the absence of a running service - the probe never reached the target host to test whether a service is listening.

Firewalk sets the TTL on probe packets to expire exactly one hop past the target firewall. A 'TTL exceeded' ICMP response on port 23 means the packet traversed the firewall and was forwarded toward the destination - confirming port 23 is not filtered. The absence of any response on ports 21 and 22 indicates those probes were dropped by the firewall before reaching the next hop, meaning those ports are blocked.

A TTL exceeded response comes from a router one hop past the firewall, not from the destination host itself, so no connection to the destination was established.