The actors behind the Emotet botnet ended a four-month hiatus by launching a malspam campaign targeting Polish- and German-speaking users.

According to ZDNet, security researcher Raashid Bhat spotted the Emotet botnet distributing new spam emails beginning on Sept. 16. Those emails contained malware-laden attachments and URLs that linked to malicious downloads. Users who downloaded or executed one of the malicious files associated with the campaign exposed themselves to the malware.

Upon completion of a successful infection, the threat enlisted each victim’s computer into a botnet that serves as a malware-as-a-service (MaaS) for attackers. Many bad actors have already leveraged this functionality to target the networks of enterprises and local governments with a variety of malicious software, especially samples of the BitPaymer and Ryuk ransomware families.

A Look Back at the Recent History of Emotet

Despite its four-month hiatus, Emotet made headlines throughout the first half of 2019. In February, researchers at Menlo Security spotted a spate of new attack campaigns that distributed the malware via URLs hosted on attacker infrastructure and traditional spam email attachments.

A couple of months later, Minerva Labs spotted the threat leveraging stolen email threads as a means of distribution. Shortly thereafter, Bleeping Computer reported on Emotet’s use of compromised connected devices as proxy command-and-control (C&C) servers. But then the malware suddenly went quiet, with Check Point not detecting any new campaigns for the majority of June.

How to Defend Against Phishing-Borne Malware

Security professionals can help defend their organizations against phishing-borne malware by integrating phishing intelligence into their security information and event management (SIEM) solution to vet attack campaigns such as spam operations. Companies should also help create an ongoing security awareness training program as part of a layered approach to maintaining their organization’s email security.