Files can be easily renamed to disguise their actual type. Programs such as Microsoft Word are "extension independent"—they will recognize and open "their" documents regardless of the file name. This poses a danger, for example, if a Word document containing a macro virus has been named "benefitsform.pdf." Word will open the file, but the file might not have been scanned if IWSVA is not set to check the true file type.

When set to IntelliScan, IWSVA will confirm a file's true type by opening the file header and checking its internally registered data type.

Only files of that type that are actually capable of being infected are scanned. For example, .gif files make up a large volume of all Web traffic, but they are known not to carry viruses. With true file type selected, after the true type has been determined, these inert file types are not scanned.