[Dave]

It could be a crawler or someone running a script, hard to tell. If you have access to your access logs then you should filter it by those IP addresses and see what they are doing.

To answer your questions:
1. You could if you think it's fishy, but you don't know whether they have a dynamic or static IP. Banning dynamic IP addresses is pretty much useless.
2. It depends on what they are doing. If it's a flood then your DDoS protection should block it. It's hard to tell from our position. Check your access logs and find out what it's doing.