unknown auth entries in log

[Xia Bin]

hi

This mornning I find some ip address listed in the "System auth log"
section in my daily root mail.

I've been new to linux and I would be glad if someone can tell me why
are those IPs listed, and most importantly: would it be a crack? If it
was, what to do next?

Thanks


------------------------------------
Connections:

   Service auth:

      66.154.80.100: 1 Time(s)
      192.168.0.1: 1 Time(s)
      212.204.214.114: 1 Time(s)
      216.55.156.62: 2 Time(s)