The Necurs botnet made the headlines at year-end sending tens of millions of spam emails daily as part of massive ransomware campaigns. The peak was reached on December 20th with over 47 million email (peaking at 5.7 million per hour) The activity of the botnet increased again on Dec. 28-29, on the first day it peaked 6.5 million messages early morning. On the next day, the Necurs Botnet sent out nearly 59 million ransomware messages.”]
Source: http://securityaffairs.co/wordpress/67356/malware/necurs-botnet-end-2017.html