DAT files and how they work
When the scanning engine searches through files looking for threats, it compares the contents of the scanned files to known threat information stored in the detection definition (DAT) files. The known threat information, called signatures, is information McAfee Labs has found and added to the DAT files.
Besides the signatures, the DAT files also includes how to clean and counteract the damage created by the detected virus. That is why it is so important to download the most recent version of DAT file used by VirusScan Enterprise.
CAUTION:
If the signature of a certain virus is not contained in any of the DAT files you have installed, that virus will not be detected by the scanning engine. Also, the scanning engine must be the latest version to be able to fully utilize the latest DAT files.
VirusScan Enterprise also uses heuristics, called Artemis, to check for suspicious files along with the DAT files. Refer to How Artemis works for more information.
The various DAT files are stored at the following path:
\Program Files\Common Files\McAfee\Engine