If you have a server running SSH, you can try the "lastb" command, which shows failed logins. Or, look in the logfile, often /var/log/secure or similar.

  root     ssh:notty    116.31.116.44    Fri Mar 10 22:27 - 22:27  (00:00)    
  root     ssh:notty    116.31.116.44    Fri Mar 10 22:27 - 22:27  (00:00)    
  ...

My personal server has 153,246 entries from this single IP, from 1 March until now.