Spam botnets: The fall of Grum and the rise of Festi

Spamhaus and partners took down the Grum botnet in July 2012, effectively neutralizing it, while observing a rapid rise in Festi (Spamnost) activity that, at its peak, accounted for ~300,000 spamming IPs in a 24-hour period and competed with Cutwail as a top spam source; Spamhaus continues to monitor and mitigate these spam botnet threats using takedowns and BGP feed protections.