Notorious spam botnet Rustock has gone quiet and security analysts aren’t sure why. The botnet ceased sending spam around 15:30 UTC, on March 16th. In 2010, Rustock was responsible for more than 44 billion spam emails per day and had more than one million bots under its control and accounted for as much as 47.5 percent of all spam. If this current stoppage is the result of a coordinated takedown it would be the largest take down of a botnet to date.”]
Source: https://www.csoonline.com/article/2127650/rustock-botnet-goes-quiet–reason-for-takedown-unclear.html