Analysis of information sources in references of the Wikipedia article "Pingback" in English language version.
This issue arises from the fact that it is possible for an attacker A to impersonate T's blog by connecting to R's blog and sending a link notification that specifies T's blog as the origination of the notification. At that point, K will automatically attempt to connect to T to download the blog post. This is called reflection. If the attacker were careful to select a URL that has a lot of information in it, this would cause amplification. In other words, for a relatively small request from the attacker (A) to the reflector, the reflector (R) will connect to the target (T) and cause a large amount of traffic. [...] On the reflector side for the 200-byte request, the response can easily be thousands of bytes – resulting in a multiplication that starts in the 10x, 20x and more. [...] To avoid overloading the reflector, multiple reflectors can be employed to scale up. Thus, the target will have their outgoing bandwidth, and possibly compute resources, exhausted. [...] Another point to consider is the compute resources tied to the target side. If considering a page that is computationally expensive to produce, it may be more efficient for the attacker to overload the CPU of a system versus the bandwidth of the connection. [...] This is not the first time a CMS, and in particular WordPress, has been used for DDoS or other malicious activity. To a very large extent, this is because WordPress appeals to users that do not have the resources to manage their websites and they often use WordPress to make their job easier. As a result, many users do not have an adequate patch management program or proper monitoring to observe irregularities in their traffic.
One enhancement WordPress added to the pingbacks in 3.7, which at least tracked the originating IP of the request. While this doesn't solve the problem, it at least allows you to trace where the calls are coming from. Unless the attacker is very, very naive however, this IP will simply trace back to another infected machine or site. Generally these requesting systems are part of a botnet to mask and distribute the requests. [...] The pingback tool within WordPress still remains an exploitable system for any WordPress site which hasn't explicitly stopped it. From a web host's perspective, this is quite frustrating.
Starting in version 3.9, WordPress started to record the IP address of where the pingback request originated. That diminished the value of using WordPress as part of an attack; the platform would now record the attackers original IP address and it would show up in the log user agent. [...] Despite the potential reduction in value with the IP logging, attackers are still using this technique. Likely because website owners rarely check the user agent logs to derive the real IP address of visitors. [...] Although it is great that WordPress is logging the attacker IP address on newer releases, we still recommend that you disable pingbacks on your site. It won't protect you from being attacked, but will stop your site from attacking others.
