Thrush
You're talking about your own network's IP addresses, as allocated to your PC's by your DSL router.

GTi_iTG
Is on about changing his outward IP address, which usually can be done by disconnecting the USB modem.
As I said though, not all ISPs allocate new IP addresses on disconnection, I could put a USB modem on my adsl line and I know it would get the same IP address, because it's fixed, doesn't change, never will.

Best thing to do, it probably to contact their tech support and ask them, if they can re-allocate you an IP address.

Re-read your first post: The other thing is that the livebox runs a firewall, so that probably blocked 90% or more of these attacks, without the livebox, you are now totally exposed, changing IP probably won't make much of a difference tbh, I doubt someone has singled you out, probably just hitting a range of IP addresses which you happen to belong to.

hth