In case anyone else found the claim of "all internet traffic" dubious - Some clarification: What they mean when they say "internet traffic" is not "internet traffic." They are referring to web traffic, as in the number of web page loads that occurred via HTTP and HTTPS, whether that's API calls or opening pages via web browsers.
That doesn't include traffic from other protocols (tor, VPNs, gaming traffic, etc), and only includes page loads from websites from which Imperva was able to gather analytics data.