Anti-spoofing techniques are used in order to stop the DDoS (Distributed Denial-of-Service) attacks that affect so many websites. To deliver these attacks, hackers are “spoofing” IP addresses, from where they send a great number of requests.
When the website server attempts to reply to the requests, it gets stalled by waiting to access servers that actually do not exist. In this case, again, it is difficult to detect the source of the attacks, therefore the only available solution is to use software that can detect these fake IP addresses and refuse the connection.