IP spoofing and spamming

In message <2.2.32.19971029014215.0069407c@max.ibm.net.il>, Hank Nussbacher wri
tes:

The Internet works because people don't abuse other's resources. If people
abuse my resources, I stop allowing the abuse. If they threaten to sue, I
laugh and tell them to go right ahead. We write our contracts so that we
can shut off people who spam, even on the first offense.

I would be interested in seeing a copy of that contract. When suits
(lawyers) get involved, how do you show that a violation has happened?
Remember, no complaint has come to you and you would have had to sniff his
line and open his smtp pkts to see he was spamming which would invoke a
countersuit.

We reserve the right to monitor our network for operation issues, and
spoofed IP addressses are a well understood secureity risk, and I would like
to think that everyone monitors and blocks spoofed address whenever they
can.
The ECPA offers some protection from monitoring, but it specifically allows
it for maintaning the systems. I'm not 100% sure that the ECPA (US only, btw,
so it probably doesn't help you), applies, but I think there is a good
basis for it applying.