DAT files and how they work

When the scanning engine searches through files it compares the contents of the files to the contents of the detection definition (DAT) files. These DAT files contain known signatures of viruses that have been found. If the scanner finds a match it uses other DAT files to determine how to clean and counteract the damage created by the detected virus.
CAUTION:
If the signature of a certain virus is not contained in any of the DAT files, 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.

The various DAT files are stored at the following path:

\Program Files\Common Files\McAfee\Engine