Bandwidth Charges and DoS/Connection trickling

All - I was wondering if any of you have had the unfortunate experience of having your connection DoS'd and/or trickled for an extended period of time resulting in a rather large (or moreover, insultingly) large excess-bandwidth charge from your ISP?. I currently have a connecton with PIPEX (soon to be changed) and work from home as a Computer Security professional. However, over the last couple of months I have noticed that the connection is being trickled (that is, an unscrupulous individual has been filling the connection with a steady stream of garbage for extended periods of time). Since the ISP counts every byte in order to monitor usage, it is inevitable that this limit will be broken rather quickly (an 8mbit connection with 30GB limit can be trickled at 4mbit in a ~3 days).

I am currently being told that it is my responsibility to pay for the bandwidth that I obviously didn't use!, in my spare time I administer systems relating to a privately owned small-scale ISP and thus know first-hand the results of DoS attacks, however, I also know that it is not policy to charge for bandwidth that is the result of a DoS in a commercial hosting environment. So my question is, why do commerical ISP's think they can charge individual ADSL customers for bandwidth that is the result of a DoS?

In reply to:

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over the last couple of months I have noticed that the connection is being trickled (that is, an unscrupulous individual has been filling the connection with a steady stream of garbage for extended periods of time).

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From which end?

Block incoming traffic responses.....