You were all right!!!
After having enable root password and manage to put a password
I have checked the syslog in /var/log/messages and I saw:
Jan 29 08:48:24 vuduo authpriv.warn login[521]: invalid password for 'root' on
'/dev/pts/2' from '78.188.196.69:39180'
Jan 29 08:38:23 vuduo authpriv.warn login[477]: invalid password for 'root' on
'/dev/pts/2' from '117.218.161.86:10553'
Jan 29 08:35:26 vuduo authpriv.warn login[435]: invalid password for 'root' on
'/dev/pts/2' from '1.34.123.62:51869'
All these addresses are from India, Turkey.....
Then I have isolated the box from internet.
A question I have: When openPli 4 is installed does the user root has no password by default? (i.e. entry in /etc/passwd like "root::0:0:root:/home/root:/bin/sh" )
This issue started end of last year after I installed OpenPli 4.0 (before that date I had a openPli 2).
Thanks for the help.
PS: My telnet is now working perfectly.