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Emotet: How can traffic-sniffing banking malware be thwarted?

A new variety of banking malware can sniff traffic from APIs. Enterprise threats expert Nick Lewis outlines how to mitigate the risk.

I'm concerned about a new breed of banking malware that seems to "sniff" traffic from APIs. How does it work, and...

is it a significant departure from previous banking malware?

Threat Response Engineer Joie Salvio of Trend Micro Inc. wrote a blog post about new banking malware dubbed Emotet that captures data over the network by "sniffing" traffic. This attack method gained popularity with the release of dsniff, where passwords and other data were captured while going over the network unencrypted. Since then, it has been a race to encrypt all data in transport and at rest.

As malware evolves, it will continue to find new places to capture, store or send data.
Nick Lewis

The latest Emotet malware added the step of monitoring data -- or "traffic sniffing" -- before it goes over the network. Other varieties of malware capture data from RAM or from keystrokes; this is an extension of these next techniques.

Emotet needs to first get installed on a victim system by a dropper or other such method. Once installed, the Emotet malware hooks Windows APIs -- just like antimalware tools hook APIs -- to capture data before it goes over the network encrypted. Emotet has functionality to decode the captured data and then store it encrypted in the registry.

As malware evolves, it will continue to find new places to capture, store or send data. Emotet has included many new functions to inject malicious DLLs that monitor traffic onto target networks and store malicious files and collected data in the registry. These features make Emotet more difficult to detect and stop. As new techniques are identified by advanced attackers -- such as storing data in slackspace or alternative data streams -- they are incorporated into modular malware to increase the effectiveness and profitability of the attack for criminals.

To protect against Emotet, enterprises should use the same steps they use to protect endpoints from malware, such as keeping up-to-date patches, not allowing users to run as an administrator, blocking spam, implementing anti-phishing security awareness and using antimalware network appliances to block malicious files from being downloaded. Enterprises should be sure to first verify that the tools used can detect this variety malware and malicious Windows API hooks.

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Next Steps

Learn more about the evolution of banking malware and how it works.

This was last published in February 2015

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