According to a slashdot reader, F-Secure has identified that the Sony Microvault USB sticks products hides a directory from the API of Windows.

The negative thing about this is that it is technically possible for malware to hide in the hidden directory which the USB sticks created.

The directory is located under “c:\windows\”. In this hidden directory, the files are also hidden that some antivirus scanners cannot scan this area of a user’s PC. Users can use the Command Prompt and they can create new hidden files within this directory. The reader also notes that there are ways to run files from this directory.

Source: Slashdot