The world’s biggest and most prolific spamming botnet is now Rustock, with a 250,000 head count of bots. The rootkit-based malware can hide from antivirus software and employs several advanced techniques to evade detection. Rustock’s developer has added new techniques to the codebase to keep the botnet alive and well. Most botnets operators are keeping their botnets smaller to remain under the radar and to avoid takedown operations. “The model seems to be fly-under-the-radar just to the point that no one cares about you,” researcher says.”]
Source: https://www.darkreading.com/attacks-breaches/the-world-s-top-spamming-botnets