There was a guy once who thought he could bypass the usual AUP and TOS of his ISP by running his very own nntp news sever for intentional abuse purposes.
Let's say I let a 'few' people in the ISP concerned (board level people, senior tech management and their publicity company) know about this after a reasonable period of reconciliation that failed.
I got the reply within 12 hours .... "this account has been terminated". That was it, period.
I truly am an EXPERT in these matters. I even phone the techs at the ISPs concerned to get their view. That is often VERY interesting, not least because they realise they are dealing with an expert abuse tracker. With modern telecoms that's no more than the cost of a local call too.
And don't think an anonymiser will help either. Been there, done that too. They don't want to attract FBI etc attention.
Graham