User unknown attack?

Timothy Barhorst timb at
Thu Nov 30 20:39:19 GMT 2006

Over the last three days, our Mailscanner e-mail server has received >
100K attempts to a single BOGUS username  ( threateningmessage at )

Sendmail always responds with a User unknown message ... but what is the
logic of sending this many messages? 

All of them come from different source addresses so I'm pretty sure it's
some kind of spamming technique.. but not the usual dictionary attack I


Should I be concerned?? 


Tim Barhorst


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