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. The attack was conducted mainly by users from China and almost all of the attackers were mobile users utilizing QQBrowser. Most of the sites being targeted were for gaming companies.
Source: https://www.bleepingcomputer.com/news/security/hyperlink-auditing-pings-being-used-to-perform-ddos-attacks/