Which of these is a method to prevent DDoS attacks?

Implementing blackhole routing is a method specifically designed to mitigate the effects of Distributed Denial of Service (DDoS) attacks. This technique involves configuring network routers to route traffic from suspected malicious IP addresses into a "black hole," effectively discarding the traffic before it can impact legitimate users and network resources. By redirecting unwanted traffic away from the target, it helps to maintain service availability for legitimate users.

In contrast, encrypting data primarily focuses on securing sensitive information rather than addressing the availability challenges posed by DDoS attacks. Similarly, using open networks exposes systems to greater risk, as it allows unrestricted access, which can potentially increase vulnerability to attacks like DDoS. While increasing storage capacity can be beneficial for managing high traffic loads in general, it does not specifically prevent DDoS attacks and may not address the underlying issue of overwhelming service requests directed at a server during such an attack. Thus, implementing blackhole routing is the focused and effective method for preventing the impact of DDoS attacks.