The Rustock Botnet was dismantled in mid March. Global spam dropped by one-third immediately after the botnet was taken down. But since March 26th the amount of data traffic hitting MessageLabs spam traps has increased despite a decline in the number of spam emails. The Cutwail botnet has been sending more spam emails with zip file attachments, the company says. Commtouch reports in its quarterly Internet Trends Report that malware sent via email increased by 400 percent in the last week of March.”]
Source: https://www.csoonline.com/article/2128051/spam-perseveres–despite-rustock-takedown.html