The Emotet Trojan has resumed activity after more than five months of absence from the threat landscape, security researchers warn.
Active for over half a decade, Emotet has evolved from a banking Trojan to information stealer and malware downloader, and has been rather quiet for the past year or so.
In September 2019, following a four-month vacation, Emotet recommenced activity with a new technique in its pocket: it was hijacking legitimate email conversations for successful spear-phishing.
The threat became quiet again at the beginning of this year, but last week security researchers observed the first malspam waves aimed at distributing the Trojan.
Just as in September, the malware’s operators are replying to existing email threads with messages that carry malicious URLs or attachments, Malwarebytes notes.
The high-volume attacks started in the early morning of July 17, 2020, but the first signs of a comeback were observed on July 13, with low volumes of malspam.
“Emotet resurfaced in a massive campaign today after being quiet for several months. The new campaign sports longtime Emotet tactics: emails carrying links or documents w/ highly obfuscated malicious macros that run a PowerShell script to download the payload from 5 download links,” Microsoft revealed on Twitter.
The Trojan was silent for 160 days before the new attack surfaced, Proofpoint explains. On July 17, approximately a quarter million Emotet-related malicious messages were observed.
The Russian-speaking threat actor behind Emotet, which is tracked as TA542, took aim at multiple verticals in the United States and the United Kingdom, security researchers reported.
On compromised machines, Emotet would often download additional modules that enable it to steal sensitive information, including login credentials and email messages, and to spread to other machines on the local network.
Emotet has great damaging potential once it has compromised a machine on the network, especially since it is known to be dropping additional malware, such as the TrickBot Trojan, or specific ransomware families.
“The real damage that an Emotet compromise causes happens when it forms alliances with other malware gangs and in particular threat actors interested in dropping ransomware,” Malwarebytes warns.
Related: Emotet Returns, Spreads via Hijacked Email Conversations
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