The recommendation is to block chat via talk or ntalk. These services enable users to chat within terminal sessions. Rationale: These services use unsecured TCP and UDP protocols and can be snooped via the network.
Solution
Disable talk and write. rmitab writesrv chmod a-rwx /usr/sbin/writesrv trustchk -u /usr/sbin/writesrv mode Default Value: ntalk is enabled