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Zeus Trojan analysis: How to decode the Zeus config.bin file

Learn how to analyze the Zeus config.bin file in order to identify targeted URLs and infected computers on your network.

Can you explain how to decode the Zeus config.bin file?

The Zeus config.bin file is used to store the Zeus Trojan configuration. The file is encrypted with RC4, so it must be unecrypted, or decoded, before it can be analyzed. ThreatExpert has a blog post on how to decode the Zeus config file along with a utility for doing so. You can also use the free OllyDebug tool for Zeus Trojan analysis and decoding the config file. The file contains the details of which URLs are targeted by the customized Zeus bot. By identifying the URLs targeted, you can further observe what account credentials were attacked. The config file also has URLs used for downloading updates, which you can use to try to identify other infected computers on your network.

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Once you have identified the targeted URLs, notify the affected websites they are being targeted so they can monitor their systems for attacks. You can also block access to these targeted websites, or only allow access from systems that require access and are clean from malware. For any account credentials compromised, you should immediately contact the financial institution to change the credentials and put a hold on any financial transactions that may have been initiated. You could also block access to the URLs used for updates to prevent updates.

This was last published in October 2011

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