Spam volumes are at their highest volumes since mid-2010. The main culprit is the Necurs botnet, which brought back a mostly outdated tactic in 2016: high-volume spam. The window of opportunity before a spam filter kicks in may only be minutes or even seconds, so Necurs has transmitted as much email as possible. The Necurs operators can afford to run such short-term campaigns “because they’ve moved towards payloads that are more profitable,” Cisco Talos Labs says.”]
Source: https://www.darkreading.com/cloud/spam-levels-spike-thanks-in-part-to-ransomware