Security Experts:

Network Spreading Capabilities Added to Emotet Trojan

Researchers at Fidelis Cybersecurity have spotted a variant of the Emotet Trojan that has what appears to be a feature designed to help the malware spread on internal networks.

The recent WannaCry and NotPetya incidents have demonstrated how efficient an attack can be if the malware includes a component that allows it to spread from one system to another. Given the success of these operations, other cybercriminals may also be looking to incorporate similar capabilities into their malware.

Emotet, also known as Geodo, is related to the Dridex and Feodo (Cridex, Bugat) malware families. Emotet has mainly served as a banking Trojan, helping cybercriminals steal banking credentials and other sensitive information from users in Europe and the United States.

In the attacks observed recently by Fidelis, Emotet has been used as a downloader for several other banking Trojans based on the victim’s geographical location.

The spreader component seen in attacks over the past month is designed to enumerate network resources in an effort to locate shares to which it can write a file and create a remote service. The service, named “Windows Defender System Service,” writes the malware to the disk and executes it.

If a shared resource is password-protected, the malware will try to guess credentials for user and administrator accounts by launching a dictionary attack.

Researchers pointed out that the network spreader component they have analyzed is packaged differently compared to the known Emotet modules, which could indicate that the spreader is a component used only by a specific group and not a direct piece of the malware.

“With the recent addition of spreading capabilities being added to ransomware it’s not at all surprising to see other malware families start to look into adding similar capabilities. It seems to be a common trend lately for malware developers to add in functionality based on what’s in the news which recently has been filled with all things wormable, which could mean this might be a continued trend for malware in the future,” said Fidelis’ Jason Reaves.

Fidelis has published a blog post containing technical details on the spreader component and indicators of compromise (IoC).

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.