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Detecting malicious file obfuscation using certutil.exe

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CertUtil.exe can be used by attackers to encode a portable executable to a certificate file, which is base64 encoded, to hide the originating file. There are many utilities cross-platform to encode using XOR, using compressed .cab files to hide contents and scripting languages that may perform similar native Windows tasks.

This search will allow you to detect when CertUtil.exe is used to encode and decode files.

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How to use Splunk software for this use case

To deploy this use case, make sure that you have the Splunk ES Content Updates installed on your Splunk Enterprise Security deployment. This extensive content library empowers you to deploy out-of-the-box security detections and analytic stories to enhance your investigations and improve your security posture. If you do not have Splunk Enterprise Security, these detections will still give you an idea of what you can accomplish with SPL in the Splunk platform or with the free app, Splunk Security Essentials.

Some of the detections that can help you with this use case include:

Next steps

Splunk OnDemand Services: Use these credit-based services for direct access to Splunk technical consultants with a variety of technical services from a pre-defined catalog. Most customers have OnDemand Services per their license support plan. Engage the ODS team at ondemand@splunk.com if you require assistance.

In addition, these Splunk resources might help you understand and implement this use case: