Spammers are turning to an old technique known as hailstorm to slip past anti-spam and anti-malware filters to deliver Dridex banking malware and Locky ransomware. The technique is a derivation of the even older snowshoe spamming technique where massive spam attacks are launched over an extended period of time from across thousands of IP addresses, but at low volumes per IP address. Cisco Talos researchers say the technique has evolved over time as well, moving from just hawking affiliate offers to new campaigns attempting to compromise business email systems and perpetrate identity theft.
Source: https://threatpost.com/new-wave-of-hailstorm-spam-pelts-inboxes/122671/