messages文件中有大量的这种信息 求说明

半人疯

/var/log/messages 中类似这样的信息很多，该怎么做呢，这些都是什么意思呢   我用的debian
另外我主机上面/var/log里面只有这个messages文件，secure、lastlog、wtmp这些都没有，是什么原因呢

Nov 24 09:17:01 localhost CRON[27253]: pam_unix(cron:session): session opened for user root by (uid=0)
Nov 24 09:17:01 localhost CRON[27253]: pam_unix(cron:session): session closed for user root
Nov 24 09:28:37 localhost -- MARK --
Nov 24 09:48:37 localhost -- MARK --
Nov 24 10:08:37 localhost -- MARK --
Nov 24 10:17:01 localhost CRON[27260]: pam_unix(cron:session): session opened for user root by (uid=0)
Nov 24 10:17:01 localhost CRON[27260]: pam_unix(cron:session): session closed for user root
Nov 24 10:28:37 localhost -- MARK --
Nov 24 10:48:37 localhost -- MARK --
Nov 24 11:08:37 localhost -- MARK --
Nov 24 11:17:01 localhost CRON[27267]: pam_unix(cron:session): session opened for user root by (uid=0)
Nov 24 11:17:01 localhost CRON[27267]: pam_unix(cron:session): session closed for user root
Nov 24 11:28:37 localhost -- MARK --
Nov 24 11:48:37 localhost -- MARK --
Nov 24 12:08:37 localhost -- MARK --
Nov 24 12:17:01 localhost CRON[27274]: pam_unix(cron:session): session opened for user root by (uid=0)

Nov 24 12:52:26 localhost dropbear[27280]: Child connection from 139.0.1.126:44978
Nov 24 12:52:29 localhost dropbear[27280]: bad password attempt for 'root' from 139.0.1.126:44978
Nov 24 12:52:30 localhost dropbear[27280]: exit before auth (user 'root', 1 fails): Disconnect received
Nov 24 12:52:30 localhost dropbear[27281]: Child connection from 139.0.1.126:45241
Nov 24 12:52:35 localhost dropbear[27281]: bad password attempt for 'root' from 139.0.1.126:45241
Nov 24 12:52:35 localhost dropbear[27281]: exit before auth (user 'root', 1 fails): Disconnect received
Nov 24 12:52:35 localhost dropbear[27282]: Child connection from 139.0.1.126:45543
Nov 24 12:52:40 localhost dropbear[27282]: bad password attempt for 'root' from 139.0.1.126:45543
Nov 24 12:52:41 localhost dropbear[27282]: exit before auth (user 'root', 1 fails): Disconnect received

[ 本帖最后由 半人疯 于 2013-11-30 10:30 编辑 ]

licess

可能没启用，或被精简掉了