https://www.bleepingcomputer.com/news/security/hyperlink-auditing-pings-being-used-to-perform-ddos-attacks/

Researchers have found that the HTML feature called hyperlink auditing, or pings, is being used to perform DDoS attacks against various sites. This feature is normally used by sites to track link clicks, but is now found to be abused by attackers to send a massive amount of web requests to sites in order to take them offline.

For those who are unfamiliar with hyperlink auditing, it is an HTML feature that allows sites to track clicks on links. To create a hyperlink auditing URL, or ping, you can simply create a normal hyperlink HTML tag, but also include a ping="[url]" variable as shown below.