A USB would be handled the same way as if it were a local workstation drive or file server location. When its inserted it will create a mount which Spirion can then scan as a local drive. A user can then perform various remediation actions such as Redact, Shred, Encrypt, etc. which you can see here in the client set of actions.
The Removable Drives button specifies that Spirion will search the currently mounted USB drives and devices. These drives are typically flash drives, thumb drives, even mp3 players. If this option is selected, the Removable Drives button on the Locations ribbon will be highlighted.
When a location has sensitive data match information in it and you wish to keep the item and securely keep the personal information, you can utilize the Encrypt feature.
The Encrypt button is located on the Main ribbon. When Spirion locates a Data Match in any of the following location types, you will be able use the Encrypt feature with encryption to protect your data such as Microsoft Office Files, Microsoft Access Databases, Compressed Files, Adobe Acrobat PDF Files, Outlook, Cloud repositories, and many other file types.
File Locations are enabled if you enable searching for Files. You may select whether you want to search within your My Computer (which includes all of your hard drives), your My Documents (including User Settings), your removable drives (any drive connected to your computer via USB), your Cloud Folders (the local storage location for folders synchronized with cloud storage services such as Dropbox or Microsoft OneDrive), Custom Folders of your choice, or entire other Remote Machines. Once specified, Spirion will search for files (for example Common File Types or a Custom file type list) and optionally Compressed Files within those drives or folders and all of their subfolders. Your currently selected option will be highlighted.