DDoS attacks disrupt or shut down web servers as well as entire networks. In contrast to a simple denial-of-service attack (DoS), distributed denial-of-service attacks (DDoS) can have an immense impact. Several computers that have been linked through bot networks simultaneously attempt to access a site or an entire network infrastructure. This can quickly lead to the failure of the servers. Typical DDoS attacks regularly seek to congest access links and overload the resources of the firewalls and web/database servers.
Some botnets already have tens of thousands of computers under their control. These computers have been infected with malicious software and are repeatedly used to launch a powerful attack, without the computers' authorized users even being aware of it. Due to the large number of computers used, it is almost impossible for an attacked website to identify the source of the attack. Likewise, in most cases it remains unclear who can be held liable for such attacks.
The attack patterns vary constantly. In addition, the frequency and the bandwidth of attacks are on the rise. Back in 2009, the majority of attacks were volume attacks, while the attack patterns since 2010 have tended towards application layer attacks and multi-vector attacks.
The average bandwidth and attack volume of DDoS attacks have been steadily increasing. The annual growth rates are already well over 200 percent.