Safe Browsing analyzes web pages with web browsers running in virtual machines. This allows us to determine if a page contains malicious content, such as Javascript meant to exploit user machines. In this particular case, Javascript and HTML resources hosted on baidu.com were replaced with Javascript that would repeatedly request resources from the attacked domains. The last time we observed injections during our measurement period was on April 7th, 2015. This is also the first time we find truncated injections in which the Javascript is cut-off and non functional.”]
Source: https://security.googleblog.com/2015/04/a-javascript-based-ddos-attack-as-seen.html