A server administrator completes a full vulnerability scan on servers. The report shows a recent vulnerability exploit when using Telnet. The server administrator cannot take the systems offline…

Uninstalling Telnet typically requires stopping the service and potentially rebooting the server, which would constitute taking the system offline and violate the no-maintenance-window constraint.

Port 22 is the standard port for SSH, not Telnet, so disabling it would break secure remote administration while leaving the Telnet vulnerability completely unaddressed.

Telnet listens on TCP port 23. Disabling port 23 on each server - via the host-based firewall or stopping the Telnet service listener - blocks all Telnet connections at the server level without requiring a reboot or taking the system offline. This approach also protects against exploitation from internal network sources, not just external ones.

Disabling port 23 only on the perimeter firewall blocks external Telnet access but leaves the servers exposed to exploitation by users or processes on the internal network.