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Detecting Windows file extension abuse

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Attackers can make users run malicious code or persist on an endpoint by targeting file extensions that users are familiar with. For example, if users see that a file ends in .doc or .docx, they will assume that it is a Microsoft Word document and expect that double-clicking will open it using winword.exe. The user will typically also assume that the .docx file is safe. Attackers take advantage of this expectation by obfuscating the true file extension.

This use case helps you detect this type of abuse of file extensions and Windows file associations by searching for the execution of files with multiple extensions in the file name, a common technique used by attackers to obscure the true file extension.

Required data

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

These Splunk resources might help you understand and implement this use case:

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 [email protected] if you would like assistance.