Analysis of 92 billion rejected emails reveals a range of simple and complex attack techniques for the last quarter of 2019.

Kelly Sheridan, Former Senior Editor, Dark Reading

February 26, 2020

4 Min Read

RSA CONFERENCE 2020 – San Francisco – Emotet is back with a bang, driving a 145% spike in threat activity throughout the fourth quarter of 2019, researchers report in a new analysis of 202 billion emails from the past quarter. Of the messages analyzed, 92 billion were rejected. 

The "Mimecast Threat Intelligence Report: RSA Conference Edition" covers data from October to December 2019 and reveals a mix of attacks ranging from low-effort, low-cost threats to advanced and targeted campaigns. Attackers are trying to take enterprise victims by surprise; this is shown by the resurgence of Emotet malware, now growing increasingly aggressive.

This isn't the first indicator Emotet is ramping up: Earlier this year, Cisco Talos researchers detected some activity against US military domains, as well as domains belonging to state and federal governments. The malware's operators reportedly compromised accounts belonging to at least one federal government employee and sent malicious spam to the victim's contact list. At the same time, Cofense analysts found an Emotet campaign targeting the United Nations.

Now its resurgence is a focal point of Mimecast's findings, which report 61 significant attack campaigns in the last quarter of 2019 — a 145% increase over the past year. Emotet was a key driver in this increase, researchers say, as it was a component in nearly every attack identified. The subscription-based malware-as-a-service model makes it accessible to a wider audience.

Researchers noticed Emotet's operators shift from fileless malware when it first reemerged to attachment-based attacks later on. "They're trying to hone their skills in the process," says Josh Douglas, vice president of threat intelligence with Mimecast. "They're changing the dynamics of how they're targeting."

Many of the significant campaigns that used Emotet have included ransomware detections. This finding, researchers say, indicates a high likelihood that attackers are focusing on ransomware delivery, especially given the attacks using ransomware in previous quarters.

File compression was the preferred attack format for the last quarter of 2019; however, researchers saw an increase in Emotet activity via .doc and .docx file formats. Compressed files allow for a more complex and potentially multimalware payload, they explain, but they also provide an easy way to hide the actual file name of any items in the container.

Emotet's activity coincided with an increase in spam, one of the four primary threat categories analyzed in this report, along with impersonation attacks, opportunistic attacks, and targeted attacks. Spam is a significant and high-volume means to distribute malware; it was especially popular in attacks against the legal, software/software-as-a-service, and banking industries. Researchers anticipate it will continue as a popular vector given the likelihood someone will fall for it.

Impersonation attacks also remain effective as attackers spoof domains, subdomains, landing pages, websites, mobile apps, and social media profiles to manipulate their victims into sharing credentials and personal data. Management/consulting, legal, and banking are the most common industries for impersonation attacks, for which detections were down 5% during the past quarter. Attackers are using more nuanced techniques such as voicemail phishing to succeed.

Researchers also noticed a difference in the more significant attacks of the last quarter. Threats targeted a wider range of companies across different sectors, and for shorter periods of time than seen in previous quarters. Specific campaigns have only spanned one- or two-day periods, as opposed to multiday campaigns detected in the past. These attacks show an uptick in the use of short-lived, high-volume, targeted and hybridized attacks against victims across sectors.

That said, the overwhelming majority of attacks are less complex and more high-volume. This is "almost certainly" an indicator of broader access to online kits that less-skilled attackers can use to deploy attack campaigns, researchers explain in their report.

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About the Author(s)

Kelly Sheridan

Former Senior Editor, Dark Reading

Kelly Sheridan was formerly a Staff Editor at Dark Reading, where she focused on cybersecurity news and analysis. She is a business technology journalist who previously reported for InformationWeek, where she covered Microsoft, and Insurance & Technology, where she covered financial services. Sheridan earned her BA in English at Villanova University. You can follow her on Twitter @kellymsheridan.

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