Spam Attack

One of my websites (Shareworld.co.uk) has been the repeated victim of spam attacks in the last few days. I have been trying to trace the attacker – the first attack came from 75.101.225.120 which, after a lookup at ip-address.com I found belongs to Amazon Web Services – Elastic Compute Cloud – this is a service provided by Amazon where users can instantly build a virtual scalable server space – the attacker clearly uses this service in order to stay anonymous. We have also had attacks from the following IP addresses: 89.149.202.119, 62.193.245.233. Hopefully I can work out a way to block these attacks even though they are coming from different IPs!!