On some adapters, like my favourite Intel, you can change the MAC address - in the driver/config tool, it's called "Locally administered address"
http://www.mynetwatchman.com/pckidiot/chap04.htm
Two caveats - if you have LAA capability in your adapter - use an approved LAA address format, and randomize the address so there's less chance of a collision with somebody else doing the same.
The address you get (after registering the new MAC address -
http://homepage.ntlworld.com/robin.d...tips/swap.html ) may be WORSE - and you are interfering with the normal functioning of the allocation scheme.
If you are under a particularly heavy and repeating probe load from an NTL IP address - report it.
http://www.ntlworld.com/netreport/
It's really only worth reporting, if it stands out against the general background - there are so many worms and opportunist probers around, that you'll never get it completely quiet.