I am running Ubuntu 12.04 server(s). I use vncserver on them. Connection works for some time after launching the server. However, if I connect after few hours or about a day later, I get "Too many security failures" error. And in between, I do not make any unsuccessful / wrong password attempt.

This almost always happens and on multiple servers.

1) Could it be some bot trying to hack it? I could not find much in the log. In fact I could not find any info even of my own attempts in the logs. Why is this happening and how can I prevent it?

2) When this happens, even waiting for some time does not work. I have to kill and start again - which often defeats the purpose of my VNC session.

Please help!

Regards,
JP