TechRepublic published a tutorial about how to quickly check to see if your Linux server is under a DDoS attack from a single IP address.
How to quickly check to see if your Linux server is under a DDoS attack from a single IP address
Jack Wallen shows you an easy way to determine if your Linux server is under a DDoS attack and how to quickly stop it.
How to quickly check to see if your Linux server is under a DDoS attack from a single IP address