Port 6789 according to Speedguide.net the port can be used by a Netsky worm variant, but is also used by the Sun cluster manager.
In fact that is how the worm replicates itself across the Internet, by using the Java software on the cluster manager software (smc-https or Solaris Management console).
Many ports are thus always attempted to be used by viruses and hackers, it is important to continually be vigilant, and cut down on the possibility of hacking attempts.
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