I don't think the claim of 25% of all traffic being botnets is far-fetched. As the internet advances cyber criminals advance. Most common users are just that...USERS, so if cyber criminals can spread their attacks over a larger network of computers but use less processes on each machine then they can potentially be more successful, because they are flying under the radar and undetected. USERS are not going to proactively protect their systems or scan/clean their systems if they do not notice a evident problem, they will operate as normal thinking all is fine while their computer is being used for criminal activities. So it is no surprise that 25% of all traffic would be involved in cyber crimes, because at least 75% of all internet users are non-techs and non-proactive when it concerns computer security.