"Unusual" Port Scans from our computer - ISP shuts us down

From: Fred Marshall (fmarshallx_at_remove_the_x.acm.org)
Date: 09/05/03 

Date: Thu, 4 Sep 2003 18:09:34 -0700

I have a couple of situations where a single ISP reports that "hostile" port
scans are emanating from our computer. The ISP action is to block our
internet connections.

I've not been able to determine what might be causing such behavior, whether
it truly represents a threat to the world or is an over-reaction by the ISP.
Googling for "port scans out", etc. and searching various antivirus sites
yields nothing that appears to address this issue.

Any suggestions how to resolve?

The first time I ran into this an up to date virus scan found nothing. We
were forced to rebuild the system - i.e. reinstall Windows and everything
else. That's an awfully time consuming process for a "maybe" threat.

I'm asking the ISP for an exact description of what they're seeing. This
has only happened a couple of times, always with commercial / retail
enterprises and only with just the one ISP out of 3 that are local. I think
both customers are on DSL - but doubt that it would matter of course.

Thanks,

Fred

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