Another reader, Tony W. was checking his logs for any activity referenced in Tony Carothers diary on UDP Port 21713.  What he found were the three ports UDP 54929, 46304 and 23010 all started being hit about the same time on his network.  When you look at the DShield graphs of these three, they are very similar to the trend on 21713.  Is there any coorelation?  I have no idea at this point.  However, while your checking your logs for 21713, look and see if these ports are showing up as well.  If anyone can get packet captures for any of these, that would be most helpful!