Connect with us

Hi, what are you looking for?



Spam “Hailstorms” Deliver Variety of Threats

Spam campaigns have evolved from sending a low number of messages for long periods of time to sending a high volume of emails over a short time span, which improves delivery rates before protection mechanisms can be triggered, Cisco Talos researchers warn.

Spam campaigns have evolved from sending a low number of messages for long periods of time to sending a high volume of emails over a short time span, which improves delivery rates before protection mechanisms can be triggered, Cisco Talos researchers warn.

Called “hailstorm” spam, the new type of spam relies on the use of a large number of sender IP addresses from all around the world. While traditional campaigns, called snowshoe attacks, show a query rate of 35 queries per hour, the DNS query volume during hailstorm attacks spikes to over 75K queries per hour, researchers say.

snowshoe spam

hailstorm spam

Charts of DNS query volume patterns for traditional snowshoe spam (Top) vs. Hailstorm Spam (Bottom) [Image Credit: Cisco]

The analysis of recent campaigns has shown that hailstorm spam is being sent from all around the world, with the United States, Germany, Netherlands, the United Kingdom and Russia being the top five countries in terms of sent emails. What’s more, these attacks also involve domains registered at a wide array of Top Level Domains (TLDs), Cisco security researchers reveal.

The initial hailstorm spam campaigns were focused on advertising products such as home-surveillance systems, flashlights, dietary supplements, and other items, and different types of services, as well as on generating sponsored traffic. However, the new attack method was used for more damaging purposes than just generating traffic to affiliate pages, as malware and phishing entered scene.

The Necurs botnet, Cisco says, is using hailstorm tactics to spread malware. Cisco researchers observed a message supposedly coming as a response to a complaint filed with the United Kingdom’s Companies House, but which distributed the TrickBot banking Trojan via a malicious attachment.

While this hailstorm malware campaign shared similarities with other similar attacks, such as the delivery of the whole campaign in a very short burst, it also showed significant differences from typical hailstorm spam campaigns, researchers say. Messages were sent from a wider range of IPs, including some addresses that did not resolve to the domain used in the From header, and the messages were more in line with traditional spam and bot behavior.

Advertisement. Scroll to continue reading.

The security researchers also managed to tie hailstorm campaigns with bursts in DNS queries with an intensity of 9,000+ queries per hour at their peak(s). “The initial spike in a hailstorm campaign stems from mail server activity caused by an influx of emails. One way to understand the life cycle of a hailstorm campaign is to look at how many mail servers are targeted with a given domain,” the researchers explain.

By looking at the mail servers targeted by a sample of 475 hailstorm domains, Cisco also determined that servers in the United States are targeted the most compared to other countries. 

“As outlined in the examples, hailstorm comes in several flavors. We expect to see it evolve over time as anti-spam systems make it harder and harder for spammers to deliver their payload,” Cisco says.

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Join security experts as they discuss ZTNA’s untapped potential to both reduce cyber risk and empower the business.


Join Microsoft and Finite State for a webinar that will introduce a new strategy for securing the software supply chain.


Expert Insights

Related Content


The easiest way for a cyber-attacker to gain access to sensitive data is by compromising an end user’s identity and credentials. Things get even...

Application Security

Fortinet on Monday issued an emergency patch to cover a severe vulnerability in its FortiOS SSL-VPN product, warning that hackers have already exploited the...

Fraud & Identity Theft

Famed hacker Kevin Mitnick has died after a battle with pancreatic cancer.  At the time of his death, he was Chief Hacking Officer at...


The North Korean APT tracked as TA444 is either moonlighting from its previous primary purpose, expanding its attack repertoire, or is being impersonated by...


The Single Most Important Part of Dealing with a Phishing Attack is Preparing for the Attack Before it Actually Happens.


Enterprise users have been warned that cybercriminals may be trying to phish their credentials by luring them with fake emails that appear to be...

Application Security

Microsoft on Tuesday pushed a major Windows update to address a security feature bypass already exploited in global ransomware attacks.The operating system update, released...

Application Security

Password management firm LastPass says the hackers behind an August data breach stole a massive stash of customer data, including password vault data that...