Is this a hacker??

[hjnet]

I´m getting belows email every day

Active System Attack Alerts
=-=-=-=-=-=-=-=-=-=-=-=-=-=
May 22 23:58:07 server1 portsentry[1193]: attackalert: Connect from host: cm61-10-9-171.hkcable.com.hk/61.10.9.171 to TCP port: 111
May 22 23:58:12 server1 portsentry[1193]: attackalert: Connect from host: cm61-10-9-171.hkcable.com.hk/61.10.9.171 to TCP port: 111
May 22 23:58:12 server1 portsentry[1193]: attackalert: Host: 61.10.9.171 is already blocked. Ignoring

and nearly at the same time, the whole server went offline and keeps offline until I restart it manually.

[haze]

Looks like someone scanning your server. I get these everyday.

[hjnet]

I´ve heard that it is useful to close all unused ports. Any Idea how I can do this??

[haze]

With IPchains, which is probably already installed on your server.