Denial of Service Attacks

The idea behind denial of service attacks is simple - the attacker tries to overload the server by trying to access the server's services. If done quickly and in large amounts, the system will invariably crash due to a loss of memory. Due to their simple nature, DOS's are used quite often in cyber vandalism attacks.

In class, we used Hping3 to overload a Windows Server 2003 instance in VirtualBox. A simple command was all that was required to push virtual CPU usage to 100%. Simultaneously, page file allocation increased at a steady rate after the DOS was started. However, it still took more than five minutes for a small instance to be overloaded, showing that DOS's are often difficult to finish on large systems. This problem can be abated, however, if multiple individuals begin DOS attacks on the same target from separate locations. This is called a distributed denial of service attack, and are usually done to disrupt large-scale websites and web services like banks and search engines, and is often undertaken by large hacker groups with political or social agendas. Understanding how denial of service attack work is essential to being an ethical hacker and web developer, as it forces individuals and businesses to develop well-scaled and secure web applications.