A server listens for TCP connections on TCP port 17. Once a connection is established a short message is sent out the connection (and any data received is thrown away). The service closes the connection after sending the quote.

Another quote of the day service is defined as a datagram based application on UDP. A server listens for UDP datagrams on UDP port 17. When a datagram is received, an answering datagram is sent containing a quote (the data in the received datagram is ignored).

An easy attack is 'pingpong' which IP spoofs a packet between two machines running qotd. This will cause them to spew characters at each other, slowing the machines down and saturating the network.

Solution:

- Under Unix systems, comment out the 'qotd' line in /etc/inetd.conf
and restart the inetd process

- Under Windows systems, set the following registry keys to 0 :
HKLM\System\CurrentControlSet\Services\SimpTCP\Parameters\EnableTcpQotd
HKLM\System\CurrentControlSet\Services\SimpTCP\Parameters\EnableUdpQotd

Then launch cmd.exe and type :

net stop simptcp
net start simptcp

To restart the service.