Not much that can be done to identify the traffic without some packet traces. Note that you can't trust the source of UDP packets in any way, so they might come from a single host even if the source address is random.
If you don't have a fixed IP the easy solution is to change your mac address, then take a new DHCP lease. That way you will get a new IP address and the traffic will be dropped in a router somewhere until an unlucky guy gets your old IP. Hopefully the one creating the traffic will have stopped by then.
You should also make sure that 1: The UDP traffic is not legit and part of some protocol your system is speaking, such as DHT 2: That it really eats up all your bandwidth. A few hundreds of pps is not enough to fill your line. Without the right tools (Wireshark is a good start) estimating how much bandwidth is being used is hard.