Protecting the video-serving infrastructure from attack requires maintaining video streams and equipment at optimal performance levels. Degradation of video streams or serving equipment can impact subscriber experience. Denial of service (DoS) or distributed DoS (DDoS) attacks are often the mechanisms for attackers to bring a video server to its knees. Such attacks flood servers with repeated illegitimate requests, robbing the video server of processing cycles to handle legitimate requests -- and eventually overwhelming the server. The attack is primarily intentional but can also be unintentional due to faulty equipment or connections. One example is faulty memory or even a loose network connection that could cause a set-top box (STB) to continually request resending of packets.
Direct subscriber interaction makes the video-serving infrastructure particularly vulnerable to DoS attacks. Stateful firewalls complement DoS protection features embedded within network devices and can be effective in monitoring the number of requests per second per subscriber. Repeated requests can be blocked by the firewall if they exceed the stated thresholds. However, due to the high bandwidth requirements of video, firewall capacities can quickly reach their limits. The demand can require large firewall farms to protect a farm of video servers. This can create network management challenges and high costs.