Please Help! How to STOP them...

Fri Jan 12 21:43:10 UTC 2007

I am reading many hundred lines similar to below mentioned?

Could you please advise me what to do and how can I make my box more secure?

Jan  9 17:54:42 localhost sshd[5130]: reverse mapping checking getaddrinfo
for bbs-83-179.189.218.on-nets.com [218.189.179.83] failed - POSSIBLE
BREAK-IN ATTEMPT!
Jan  9 17:54:42 localhost sshd[5130]: Invalid user sysadmin from
218.189.179.83

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Thanks!

BR / vj