GEN:SID 1:717
Message TELNET not on console
Summary This event is generated when a failed remote telnet connection occurs using the root account.
Impact Failed root access.  This event indicates that an attacker tried an failed to connect to a telnet server using the root account.

Detailed Information Telnet servers can be configured to disallow connections using the root account.  If root privileges are required, the root user must log on to the telnet server's console directly.  A failed telnet connection using the root account will generate an error message.
Affected Systems Telnet servers.
Attack Scenarios An attacker may attempt to log on to a telnet server using the root account.
Ease of Attack Simple
Corrective Action Disable root logins using telnet.

Consider using Secure Shell instead of telnet.

Block inbound telnet access if it is not required.
Additional References Arachnids:
http://www.whitehats.com/info/IDS365
Rule References arachnids: 365